Bioimaging Modalities Research Articles

Gold Nanomaterials for Imaging-Guided Near-Infrared in vivo Cancer Therapy.

In recent years, tremendous efforts have been devoted into the fields of valuable diagnosis and anticancer treatment, such as real-time imaging, photothermal, and photodynamic therapy, and drug delivery. As promising nanocarriers, gold nanomaterials have attracted widespread attention during the last two decades for cancer diagnosis and therapy due to their prominent properties. With the development of nanoscience and nanotechnology, the fascinating bio-applications of functionalized gold nanomaterials have been gradually developed from in vitro to in vivo. This mini-review emphasizes some recent advances of photothermal imaging (PTI), surface-enhanced Raman scattering (SERS) imaging, and photoacoustic imaging (PAI)-guided based on gold nanomaterials in vivo therapy in near infrared region (>800 nm). We focus on the fundamental strategies, characteristics of bio-imaging modalities involving the advantages of multiples imaging modalities for cancer treatment, and then highlight a few examples of each techniques. Finally, we discuss the perspectives and challenges in gold nanomaterial-based cancer therapy.

A Library of Potential Nanoparticle Contrast Agents for X-Ray Fluorescence Tomography Bioimaging.

Nanoparticles (NPs) have been used as contrast agents for several bioimaging modalities. X-ray fluorescence (XRF) tomography can provide sensitive and quantitative 3D detection of NPs. With spectrally matched NPs as contrast agents, we demonstrated earlier in a laboratory system that XRF tomography could achieve high-spatial-resolution tumor imaging in mice. Here, we present the synthesis, characterization, and evaluation of a library of NPs containing Y, Zr, Nb, Rh, and Ru that have spectrally matched K-shell absorption for the laboratory scale X-ray source. The K-shell emissions of these NPs are spectrally well separated from the X-ray probe and the Compton background, making them suitable for the lab-scale XRF tomography system. Their potential as XRF contrast agents is demonstrated successfully in a small-animal equivalent phantom, confirming the simulation results. The diversity in the NP composition provides a flexible platform for a better design and biological optimization of XRF tomography nanoprobes.

A Geant4-based Monte Carlo study of a benchtop multi-pinhole X-ray fluorescence computed tomography imaging.

BackgroundX-ray fluorescence (XRF) computed tomography (XFCT) has shown promise for molecular imaging of metal nanoparticles such as gold nanoparticles (GNPs) and benchtop XFCT is under active development due to its easy access, low-cost instrumentation and operation.PurposeTo validate the performance of a Geant4-based Monte Carlo (MC) model of a benchtop multi-pinhole XFCT system for quantitative imaging of GNPs.MethodsThe MC mode consisted of a fan-beam x-ray source (125 kVp), which was used to stimulate the emission of XRF from the GNPs, a phantom (3 cm in diameter) which included six or nine inserts (3 mm in diameter), each of which contained the same (1 wt. %) or various (0.08–1 wt. %) concentrations of GNPs, a multi-pinhole collimator which could acquire multiple projections simultaneously and a one-sided or two-sided two-dimensional (2D) detector. Various pinhole diameters (3.7, 2, 1, 0.5 and 0.25 mm) and various particle numbers (20, 40, 80 and 100 billion) were simulated and the results for single pinhole and multi-pinhole (9 pinholes) imaging were compared.ResultsThe image resolution for a 1 mm multi-pinhole was between 0.88 and 1.38 mm. The detection limit for multi-pinhole operation was about 0.09 wt. %, while that for the single pinhole was about 0.13 wt. %. For a fixed number of pinholes, noise increased with decreasing number of photons.ConclusionThe MC mode could acquire 2D slice images of the object without rotation and demonstrated that a multi-pinhole XFCT imaging system could be a potential bioimaging modality for nanomedical applications.

Optoacoustic imaging at kilohertz volumetric frame rates.

State-of-the-art optoacoustic tomographic imaging systems have been shown to attain three-dimensional (3D) frame rates of the order of 100 Hz. While such a high volumetric imaging speed is beyond reach for other bio-imaging modalities, it may still be insufficient to accurately monitor some faster events occurring on a millisecond scale. Increasing the 3D imaging rate is usually hampered by the limited throughput capacity of the data acquisition electronics and memory used to capture vast amounts of the generated optoacoustic (OA) data in real time. Herein, we developed a sparse signal acquisition scheme and a total-variation-based reconstruction approach in a combined space-time domain in order to achieve 3D OA imaging at kilohertz rates. By continuous monitoring of freely swimming zebrafish larvae in a 3D region, we demonstrate that the new approach enables significantly increasing the volumetric imaging rate by using a fraction of the tomographic projections without compromising the reconstructed image quality. The suggested method may benefit studies looking at ultrafast biological phenomena in 3D, such as large-scale neuronal activity, cardiac motion, or freely behaving organisms.

Upconversion in photodynamic therapy: plumbing the depths.

Photodynamic therapy (PDT) involves the combination of non-toxic dyes called photosensitizers (PS) and harmless visible light that interact with ambient oxygen to give reactive oxygen species (ROS) that can damage biomolecules and kill cells. PDT has mostly been developed as a cancer therapy but can also be used as an antimicrobial approach against localized infections. However even the longest wavelength used for exciting PS (in the 700 nm region) has relatively poor tissue penetration, and many PS are much better excited by blue and green light. Therefore upconversion nanoparticles (UCNPs) have been investigated in order to allow deeper-penetrating near-infrared light (980 nm or 810 nm) to be used for PDT. NaYF4 nanoparticles doped with Yb3+ and Er3+ or with Tm3+ and Er3+ have been attached to PS either by covalent conjugation, or by absorption to the coating or shell (used to render the UCNPs biocompatible). Forster resonance energy transfer to the PS then allows NIR light energy to be transduced into ROS leading to cell killing and tumor regression. Some studies have experimentally demonstrated the deep tissue advantage of UCNP-PDT. Recent advances have included dye-sensitized UCNPs and UCNPs coupled to PS, and other potentially synergistic drug molecules or techniques. A variety of bioimaging modalities have also been combined with upconversion PDT. Further studies are necessary to optimize the drug-delivery abilities of the UCNPs, improve the quantum yields, allow intravenous injection and tumor targeting, and ensure lack of toxicity at the required doses before potential clinical applications.

Visualizing Angiogenesis by Multiphoton Microscopy In Vivo in Genetically Modified 3D-PLGA/nHAp Scaffold for Calvarial Critical Bone Defect Repair.

The reconstruction of critically sized bone defects remains a serious clinical problem because of poor angiogenesis within tissue-engineered scaffolds during repair, which gives rise to a lack of sufficient blood supply and causes necrosis of the new tissues. Rapid vascularization is a vital prerequisite for new tissue survival and integration with existing host tissue. The de novo generation of vasculature in scaffolds is one of the most important steps in making bone regeneration more efficient, allowing repairing tissue to grow into a scaffold. To tackle this problem, the genetic modification of a biomaterial scaffold is used to accelerate angiogenesis and osteogenesis. However, visualizing and tracking in vivo blood vessel formation in real-time and in three-dimensional (3D) scaffolds or new bone tissue is still an obstacle for bone tissue engineering. Multiphoton microscopy (MPM) is a novel bio-imaging modality that can acquire volumetric data from biological structures in a high-resolution and minimally-invasive manner. The objective of this study was to visualize angiogenesis with multiphoton microscopy in vivo in a genetically modified 3D-PLGA/nHAp scaffold for calvarial critical bone defect repair. PLGA/nHAp scaffolds were functionalized for the sustained delivery of a growth factor pdgf-b gene carrying lentiviral vectors (LV-pdgfb) in order to facilitate angiogenesis and to enhance bone regeneration. In a scaffold-implanted calvarial critical bone defect mouse model, the blood vessel areas (BVAs) in PHp scaffolds were significantly higher than in PH scaffolds. Additionally, the expression of pdgf-b and angiogenesis-related genes, vWF and VEGFR2, increased correspondingly. MicroCT analysis indicated that the new bone formation in the PHp group dramatically improved compared to the other groups. To our knowledge, this is the first time multiphoton microscopy was used in bone tissue-engineering to investigate angiogenesis in a 3D bio-degradable scaffold in vivo and in real-time.

Visualizing Angiogenesis by Multiphoton Microscopy<em> In Vivo</em> in Genetically Modified 3D-PLGA/nHAp Scaffold for Calvarial Critical Bone Defect Repair

The reconstruction of critically sized bone defects remains a serious clinical problem because of poor angiogenesis within tissue-engineered scaffolds during repair, which gives rise to a lack of sufficient blood supply and causes necrosis of the new tissues. Rapid vascularization is a vital prerequisite for new tissue survival and integration with existing host tissue. The de novo generation of vasculature in scaffolds is one of the most important steps in making bone regeneration more efficient, allowing repairing tissue to grow into a scaffold. To tackle this problem, the genetic modification of a biomaterial scaffold is used to accelerate angiogenesis and osteogenesis. However, visualizing and tracking in vivo blood vessel formation in real-time and in three-dimensional (3D) scaffolds or new bone tissue is still an obstacle for bone tissue engineering. Multiphoton microscopy (MPM) is a novel bio-imaging modality that can acquire volumetric data from biological structures in a high-resolution and minimally-invasive manner. The objective of this study was to visualize angiogenesis with multiphoton microscopy in vivo in a genetically modified 3D-PLGA/nHAp scaffold for calvarial critical bone defect repair. PLGA/nHAp scaffolds were functionalized for the sustained delivery of a growth factor pdgf-b gene carrying lentiviral vectors (LV-pdgfb) in order to facilitate angiogenesis and to enhance bone regeneration. In a scaffold-implanted calvarial critical bone defect mouse model, the blood vessel areas (BVAs) in PHp scaffolds were significantly higher than in PH scaffolds. Additionally, the expression of pdgf-b and angiogenesis-related genes, vWF and VEGFR2, increased correspondingly. MicroCT analysis indicated that the new bone formation in the PHp group dramatically improved compared to the other groups. To our knowledge, this is the first time multiphoton microscopy was used in bone tissue-engineering to investigate angiogenesis in a 3D bio-degradable scaffold in vivo and in real-time.

Pinhole X-ray fluorescence imaging of gadolinium and gold nanoparticles using polychromatic X-rays: a Monte Carlo study.

This work aims to develop a Monte Carlo (MC) model for pinhole K-shell X-ray fluorescence (XRF) imaging of metal nanoparticles using polychromatic X-rays. The MC model consisted of two-dimensional (2D) position-sensitive detectors and fan-beam X-rays used to stimulate the emission of XRF photons from gadolinium (Gd) or gold (Au) nanoparticles. Four cylindrical columns containing different concentrations of nanoparticles ranging from 0.01% to 0.09% by weight (wt%) were placed in a 5 cm diameter cylindrical water phantom. The images of the columns had detectable contrast-to-noise ratios (CNRs) of 5.7 and 4.3 for 0.01 wt% Gd and for 0.03 wt% Au, respectively. Higher concentrations of nanoparticles yielded higher CNR. For 1×1011 incident particles, the radiation dose to the phantom was 19.9 mGy for 110 kVp X-rays (Gd imaging) and 26.1 mGy for 140 kVp X-rays (Au imaging). The MC model of a pinhole XRF can acquire direct 2D slice images of the object without image reconstruction. The MC model demonstrated that the pinhole XRF imaging system could be a potential bioimaging modality for nanomedicine.

Enhancing T1 magnetic resonance imaging contrast with internalized gadolinium(III) in a multilayer nanoparticle

Multifunctional nanoparticles for biomedical applications have shown extraordinary potential as contrast agents in various bioimaging modalities, near-IR photothermal therapy, and for light-triggered therapeutic release processes. Over the past several years, numerous studies have been performed to synthesize and enhance MRI contrast with nanoparticles. However, understanding the MRI enhancement mechanism in a multishell nanoparticle geometry, and controlling its properties, remains a challenge. To systematically examine MRI enhancement in a nanoparticle geometry, we have synthesized MRI-active Au nanomatryoshkas. These are Au core-silica layer-Au shell nanoparticles, where Gd(III) ions are encapsulated within the silica layer between the inner core and outer Au layer of the nanoparticle (Gd-NM). This multifunctional nanoparticle retains its strong near-IR Fano-resonant optical absorption properties essential for photothermal or other near-IR light-triggered therapy, while simultaneously providing increased T1 contrast in MR imaging by concentrating Gd(III) within the nanoparticle. Measurements of Gd-NM revealed a strongly enhanced T1 relaxivity (r1 ∼ 24 mM-1⋅s-1) even at 4.7 T, substantially surpassing conventional Gd(III) chelating agents (r1 ∼ 3 mM-1⋅s-1 at 4.7 T) currently in clinical use. By varying the thickness of the outer gold layer of the nanoparticle, we show that the observed relaxivities are consistent with Solomon-Bloembergen-Morgan (SBM) theory, which takes into account the longer-range interactions between the encapsulated Gd(III) and the protons of the H2O molecules outside the nanoparticle. This nanoparticle complex and its MRI T1-enhancing properties open the door for future studies on quantitative tracking of therapeutic nanoparticles in vivo, an essential step for optimizing light-induced, nanoparticle-based therapies.

Photoacoustic Drug Delivery.

Photoacoustic (PA) technology holds great potential in clinical translation as a new non-invasive bioimaging modality. In contrast to conventional optical imaging, PA imaging (PAI) enables higher resolution imaging with deeper imaging depth. Besides applications for diagnosis, PA has also been extended to theranostic applications. The guidance of PAI facilitates remotely controlled drug delivery. This review focuses on the recent development of PAI-mediated drug delivery systems. We provide an overview of the design of different PAI agents for drug delivery. The challenges and further opportunities regarding PA therapy are also discussed.

In vivo gastrointestinal drug-release monitoring through second near-infrared window fluorescent bioimaging with orally delivered microcarriers

Non-invasive monitoring of gastrointestinal drug release in vivo is extremely challenging because of the limited spatial resolution and long scanning time of existing bioimaging modalities, such as X-ray radiation and magnetic resonance. Here, we report a novel microcarrier that can retain drugs and withstand the harsh conditions of gastrointestinal tract. Significantly, we can track the microcarrier fate and semi-quantitatively monitor the content of drug released in vivo in real time by measuring the fluorescence signals in the second near-infrared window of lanthanide-based downconversion nanoparticles with an absorption competition-induced emission bioimaging system. The microcarriers show a prolonged residence time of up to 72 h in the gastrointestinal tract, releasing up to 62% of their content. Moreover, minimal deposition of the microcarriers is found in non-target organs, such as the liver, spleen and kidney. These findings provide novel insights for the development of therapeutic and bioimaging strategies of orally administered drugs.

Performance Characterization of a Switchable Acoustic Resolution and Optical Resolution Photoacoustic Microscopy System.

Photoacoustic microscopy (PAM) is a scalable bioimaging modality; one can choose low acoustic resolution with deep penetration depth or high optical resolution with shallow imaging depth. High spatial resolution and deep penetration depth is rather difficult to achieve using a single system. Here we report a switchable acoustic resolution and optical resolution photoacoustic microscopy (AR-OR-PAM) system in a single imaging system capable of both high resolution and low resolution on the same sample. Lateral resolution of 4.2 µm (with ~1.4 mm imaging depth) and lateral resolution of 45 μm (with ~7.6 mm imaging depth) was successfully demonstrated using a switchable system. In vivo blood vasculature imaging was also performed for its biological application.

First Person Bioimage: An Online Tool for Presentation and Publication of Volumetric Data

New microscopy techniques (e.g. SPIM, 3D STORM, OPT, etc.) and many other 3D bioimaging modalities (tomographic EM, MRI, CT, etc.) generate terabytes of volumetric data. Whilst highly specialized software packages are available for the analysis and visualization of such data, their use requires specialized skills and they are often costly. Furthermore the capacity to share data and allow interactive exploration by third parties is highly limited.

Silicon nanocrystals: physical properties and potential biomedical applications

Silicon (Si) nanocrystals (NCs) possess photoluminescence at room temperature and promising propertiesfor biomedical applications as bioimaging and various therapeutic modalities. The photodynamic therapyapplication is based on an ability of Si-NCs to sensitize the generation of reactive oxygen species underillumination. The sonodynamic therapy with Si-NCs can be realized due to their properties to activate thecavitation followed by destruction of cancer cells and tumors. Furthermore, Si-NCs in aqueous mediaunder electromagnetic radiofrequency irradiation can activate the heat release that is promising for thehyperthermia treatment of cancer. This paper reviews the physical properties of Si NCs, which areessential for their applications both in medical diagnostics and therapy. In the paper the properties of Si-NCs and nanoparticles (NPs) are analyzed to reveal their potential for biomedical applications. Besidesthe data on physical properties of Si-NCs and NPs the results of biomedical investigations of thesenanomaterials are also discussed.

Five colour variants of bright luminescent protein for real-time multicolour bioimaging.

Luminescence imaging has gained attention as a promising bio-imaging modality in situations where fluorescence imaging cannot be applied. However, wider application to multicolour and dynamic imaging is limited by the lack of bright luminescent proteins with emissions across the visible spectrum. Here we report five new spectral variants of the bright luminescent protein, enhanced Nano-lantern (eNL), made by concatenation of the brightest luciferase, NanoLuc, with various colour hues of fluorescent proteins. eNLs allow five-colour live-cell imaging, as well as detection of single protein complexes and even single molecules. We also develop an eNL-based Ca2+ indicator with a 500% signal change, which can image spontaneous Ca2+ dynamics in cardiomyocyte and neural cell models. These eNL probes facilitate not only multicolour imaging in living cells but also sensitive imaging of a wide repertoire of proteins, even at very low expression levels.

Carbon dots incorporated polymeric hydrogels as multifunctional platform for imaging and induction of apoptosis in lung cancer cells

Multifunctional hydrogels offer a seemingly efficient system for delivery of drugs and bioimaging modalities. The present study deals with the facile development of chitosan-based hydrogel formulation composed of highly fluorescent carbon dots (CDs) and loaded with a model anticancer drug, 5-Fluorouracil (5-FU). Herein, CDs were embedded firmly within the hydrogel matrices (CD-HY) via non-covalent interactions during the ionic cross-linking reaction. Furthermore, these hydrogels could effectively encapsulate 5-FU through hydrophobic interactions to form 5-FU@CD-HY. In this way, it was possible to combine the merits of both CDs and 5-FU on a common platform for monitoring the cellular uptake as well as therapeutic effects. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) illustrated the porous nature and formation of 5-FU@CD-HY. Besides, functional characteristics of 5-FU@CD-HY such as surface area, mechanical strength, swelling behavior and drug release were investigated. In vitro studies revealed the multifunctional aspects of 5-FU@CD-HY in monitoring the cellular uptake and inflicting apoptosis in A549 cells. Green fluorescence of CDs in 5-FU@CD-HY aided the qualitative and quantitative assessment of cellular uptake. In addition to this, the fluorescence of CDs could be used to detect apoptosis instigated by 5-FU, eliminating the need for multiplex dyes. Induction of apoptosis in 5-FU@CD-HY treated cells was evidenced by changes in cell cycle distributions and visualization of characteristic apoptotic bodies through FE-SEM. Apoptotic gene expression studies further elucidate the molecular mechanism involved in eliciting apoptosis. Thus, hydrogels mediated integration of fluorescent CDs with chemotherapeutic agents provides a new dimension for the potential use of hydrogels in cancer theranostics.

Joint Reconstruction of Absorbed Optical Energy Density and Sound Speed Distributions in Photoacoustic Computed Tomography: A Numerical Investigation.

Photoacoustic computed tomography (PACT) is a rapidly emerging bioimaging modality that seeks to reconstruct an estimate of the absorbed optical energy density within an object. Conventional PACT image reconstruction methods assume a constant speed-of-sound (SOS), which can result in image artifacts when acoustic aberrations are significant. It has been demonstrated that incorporating knowledge of an object's SOS distribution into a PACT image reconstruction method can improve image quality. However, in many cases, the SOS distribution cannot be accurately and/or conveniently estimated prior to the PACT experiment. Because variations in the SOS distribution induce aberrations in the measured photoacoustic wavefields, certain information regarding an object's SOS distribution is encoded in the PACT measurement data. Based on this observation, a joint reconstruction (JR) problem has been proposed in which the SOS distribution is concurrently estimated along with the sought-after absorbed optical energy density from the photoacoustic measurement data. A broad understanding of the extent to which the JR problem can be accurately and reliably solved has not been reported. In this work, a series of numerical experiments is described that elucidate some important properties of the JR problem that pertain to its practical feasibility. To accomplish this, an optimization-based formulation of the JR problem is developed that yields a non-linear iterative algorithm that alternatively updates the two image estimates. Heuristic analytic insights into the reconstruction problem are also provided. These results confirm the ill-conditioned nature of the joint reconstruction problem that will present significant challenges for practical applications.

COMPRESSIVE SAMPLING MULTISPECTRAL IMAGING AND UNMIXING METHOD FOR FLUORESCENT IMAGING

Multispectral imaging is an important tool for understanding composite materials in many disciplines. Spectral unmixing enables the determination of individual fluorophore distributions. Due to the dispersive nature of biomaterials the observed spectra of fluorescent dyes is unknown. Spectral unmixing can be accomplished for unknown endmember spectra using minimum volume simplex analysis (MVSA). Compressive sampling (CS) is a method to reduce the computational cost of operating on sparse data sets and can be performed efficiently using NESTA based on Nesterov’s algorithm. Here we demonstrate that NESTA and MVSA can be combined with a denoising threshold to create a compressive sampling and multispectral unmixing (CSMIU) method that enables efficient bioimaging and unmixing with high levels of accuracy (spectral angle distances (SADs) < 0.05). This CSMIU method may potentially enable broadband and in vivo bioimaging modalities. © 2016, Electromagnetics Academy. All rights reserved.

Current and predicted demographics of high myopia and an update of its associated pathological changes.

Excessive axial elongation of the eye in high myopia can cause biomechanical stretching leading to various ocular complications. The purpose of this review is to provide an update on various pathologic changes, especially in the chorio-retina and sclera that have been reported recently using advanced ophthalmic bio-imaging modalities such as optical coherence tomography, magnetic resonance imaging and fundus photography. The prevalence rates of pathologic myopia (myopic retinopathy and maculopathy) mirror the prevalence rates of high myopia as the risks of pathologic myopia increase with high myopia. Peripapillary and sub-foveal choroidal thinning, scleral thinning, and deformed/irregular eye shapes were found to be strongly associated with various pathologic myopic lesions, especially with posterior staphyloma and chorio-retinal atrophy. Considering the increasing prevalence rate of myopia and pathologic myopia, these degenerative changes are likely to increase dramatically over the next few decades due to the rapid growth in the number of individuals with high myopia and the ageing population. The current prevalence rates of pathologic myopia in older adults might have significantly underestimated the future prevalence rates and warrants age of onset of myopia being considered a major risk factor for pathologic myopia. Using advanced technology, identification of novel quantifiable chorio-retinal and scleral parameters in pathologic myopia would help to identify people at risk of developing pathologic myopia and potentially may revolutionise the management of myopia especially in risk prognostication and monitoring of disease progression.

Trastuzumab guided nanotheranostics: A lipid based multifunctional nanoformulation for targeted drug delivery and imaging in breast cancer therapy

Nowadays, emerging aspects of cancer therapy involve both diagnostic and therapeutic modules in a single setting. Targeted theranostic nanoplatforms have emerged globally as frontier research for the improvement of cancer therapy. Trastuzumab (Tmab), a humanized monoclonal antibody is now being used to target human epidermal growth factor receptor-2 (HER 2) positive cancer cells. In the present study, we have analysed the imaging and theragnosis potentiality of Tmab functionalized lipid based nanoparticles (NPs) loaded with anticancer drug rapamycin and imaging agent (quantum dots) for targeted cancer therapy and imaging. The therapeutic evaluation of drug loaded NPs were evaluated through various in vitro cellular studies. The results showed enhanced therapeutic efficacy of targeted drug loaded NPs over native drug and unconjugated NPs in HER 2 positive SKBR 3 breast cancer cell line. Moreover, exploration of the therapeutic benefits of rapamycin loaded Tmab conjugated NPs (Tmab-rapa-NPs) at molecular level, revealed augmented down regulation of mTOR signalling pathway thereby, inducing more cell death. Above all, our targeted multifunctional NPs have shown an excellent bio-imaging modality both in 2D monolayer and 3D tumor spheroid model. Thus, we can anticipate that such a multimodal nanotheranostic approach may be a useful tool for better cancer management in future.