Showing papers by "Qingming Luo published in 2010"

Micro-Optical Sectioning Tomography to Obtain a High-Resolution Atlas of the Mouse Brain

Abstract: The neuroanatomical architecture is considered to be the basis for understanding brain function and dysfunction. However, existing imaging tools have limitations for brainwide mapping of neural circuits at a mesoscale level. We developed a micro-optical sectioning tomography (MOST) system that can provide micrometer-scale tomography of a centimeter-sized whole mouse brain. Using MOST, we obtained a three-dimensional structural data set of a Golgi-stained whole mouse brain at the neurite level. The morphology and spatial locations of neurons and traces of neurites could be clearly distinguished. We found that neighboring Purkinje cells stick to each other.

HDL-mimicking peptide-lipid nanoparticles with improved tumor targeting.

Abstract: Targeted delivery of intracellularly active diagnostics and therapeutics in vivo is a major challenge in cancer nanomedicine. A nanocarrier should possess long circulation time yet be small and stable enough to freely navigate through interstitial space to deliver its cargo to targeted cells. Herein, it is shown that by adding targeting ligands to nanoparticles that mimic high-density lipoprotein (HDL), tumor-targeted sub-30-nm peptide-lipid nanocarriers are created with controllable size, cargo loading, and shielding properties. The size of the nanocarrier is tunable between 10 and 30 nm, which correlates with a payload of 15-100 molecules of fluorescent dye. Ligand-directed nanocarriers targeting epidermal growth factor receptor (EGFR) are confirmed both in vitro and in vivo. The nanocarriers show favorable circulation time, tumor accumulation, and biodistribution with or without the targeting ligand. The EGFR targeting ligand is proved to be essential for the EGFR-mediated tumor cell uptake of the nanocarriers, a prerequisite of intracellular delivery. The results demonstrate that targeted HDL-mimetic nanocarriers are useful delivery vehicles that could open new avenues for the development of clinically viable targeted nanomedicine.

Imaging dermal blood flow through the intact rat skin with an optical clearing method

Abstract: Noninvasive detection of skin microcirculation is very significant for clinical diagnosis and therapy of peripheral vascular disease. In this study, an optical clearing method enables a laser speckle contrast imaging (LSCI) technique to image dermal blood flow through intact rat skin. The optical clearing effect of rat skin in vitro caused by a mixture of PEG-400 and Thiazone is evaluated by a commercially available spectrophotometer with an integrating sphere. A LSCI system is applied to image the dermal blood flow of in vivo rat skin after topical treatment of the agents. The results show that the reduced scattering coefficient (630 nm) is down to 60% of the initial value after 40 min of topical treatment of the mixture on skin in vitro. In vivo experimental results show that a 12-min treatment of the mixture on the epidermis can make the skin transparent and dermal vessels can be observed, while treatment with pure PEG-400 cannot. The process of skin optical clearing lasts, and the skin can be recovered by treatment of saline solution. Because optical clearing decreases the temporal contrast, dermal blood flow can be obtained by the laser speckle contrast imaging technique.

Spatiotemporal laser speckle contrast analysis for blood flow imaging with maximized speckle contrast.

Abstract: Laser speckle contrast imaging is a technique used for imaging blood flow without scanning. Though several studies have attempted to combine spatial and temporal statistics of laser speckle images for reducing image noise as well as preserving acceptable spatiotemporal resolution, the statistical accuracy of these spatiotemporal methods has not been thoroughly compared. Through numerical simulation and animal experiments, this study investigates the changes in the mean speckle contrast values and the relative noise of the speckle contrast images computed by these methods with various numbers of frames and spatial windows. The simulation results show that the maximum relative error of the mean speckle contrast computed by the spatiotemporal laser speckle contrast analysis (STLASCA) method, in which the speckle contrast images are computed by analyzing the 3-D spatiotemporal speckle image cube, is approximately 5%, while it is higher than 13% for other methods. Changes in the mean speckle contrast values and the relative noise computed by these methods for animal experiment data are consistent with the simulation results. Our results demonstrate that STLASCA achieves more accurate speckle contrast, and suggest that STLASCA most effectively utilizes the number of pixels, thus achieving maximized speckle contrast, and thereby maximizing the variation of the laser speckle contrast image.

Ultra-fast, high-precision image analysis for localization-based super resolution microscopy.

Abstract: Localization-based super resolution microscopy holds superior performances in live cell imaging, but its widespread use is thus far mainly hindered by the slow image analysis speed. Here we show a powerful image analysis method based on the combination of the maximum likelihood algorithm and a Graphics Processing Unit (GPU). Results indicate that our method is fast enough for real-time processing of experimental images even from fast EMCCD cameras working at full frame rate without compromising localization precision or field of view. This newly developed method is also capable of revealing movements from the images immediately after data acquisition, which is of great benefit to live cell imaging.

Mcvm: monte carlo modeling of photon migration in voxelized media

Abstract: The Monte Carlo code MCML (Monte Carlo modeling of light transport in multi-layered tissue) has been the gold standard for simulations of light transport in multi-layer tissue, but it is ineffective in the presence of three-dimensional (3D) heterogeneity. New techniques have been attempted to resolve this problem, such as MCLS, which is derived from MCML, and tMCimg, which draws upon image datasets. Nevertheless, these approaches are insufficient because of their low precision or simplistic modeling. We report on the development of a novel model for photon migration in voxelized media (MCVM) with 3D heterogeneity. Voxel crossing detection and refractive-index-unmatched boundaries were considered to improve the precision and eliminate dependence on refractive-index-matched tissue. Using a semi-infinite homogeneous medium, steady-state and time-resolved simulations of MCVM agreed well with MCML, with high precision (~100%) for the total diffuse reflectance and total fractional absorption compared to those of tMCimg (< 70%). Based on a refractive-index-matched heterogeneous skin model, the results of MCVM were found to coincide with those of MCLS. Finally, MCVM was applied to a two-layered sphere with multi-inclusions, which is an example of a 3D heterogeneous media with refractive-index-unmatched boundaries. MCVM provided a reliable model for simulation of photon migration in voxelized 3D heterogeneous media, and it was developed to be a flexible and simple software tool that delivers high-precision results.

Enhancement of skin optical clearing efficacy using photo-irradiation

Abstract: Background and Objectives Tissue optical clearing technique based on immersion of tissues into optical clearing agents (OCAs) can reduce the scattering and enhance the penetration of light in tissue. However, the barrier function of epidermis limits the penetration of OCAs, and hence is responsible for the poor optical clearing efficacy of skin by topical action. In this study, a variety of light irradiation was applied to increase permeability of agents in skin and improve the optical clearing efficacy. Study Design/Materials and Methods Different light sources with different dose, i.e, CO2 laser, Nd:YAG laser (532 and 1,064 nm) with different pulse modes and Intense Pulsed Light (IPL) (400–700 and 560–950 nm) were used to irradiate rat skin in vivo, and then glycerol was applied onto the irradiated zone. VIS–NIR spectrometer was utilized to monitor the changes of reflectance. In vitro skin samples were also irradiated by Q-switched Nd:YAG laser (1,064 nm) and then treated by glycerol for 10–60 minutes. Based on the measurement of the reflectance and transmittance of the samples, the optical properties of skin and penetration depth of light were calculated. Results Results show that photo-irradiation with appropriate dose combining with the following glycerol treatment is able to reduce in vivo skin reflectance. Compared with the control group, the maximal changes in reflectance are ninefold at 575 nm and eightfold at 615 nm, respectively, which were caused by Q-switched 1,064-nm Nd:YAG laser irradiation and following glycerol treatment. The results for in vitro skin demonstrate that the joint action can significantly increase the optical penetration depth in samples. Conclusions The combination of Q-switched Nd:YAG (1,064 nm) laser and glycerol could enhance optical skin clearing efficacy significantly. This study provides a non-invasive way to improve the optical clearing of skin, which will benefit the skin optical therapy. Lasers Surg. Med. 42:132–140, 2010. © 2010 Wiley-Liss, Inc.

Combined system of fluorescence diffuse optical tomography and microcomputed tomography for small animal imaging.

Abstract: We developed a dual-modality system that combines fluorescence diffuse optical tomography (fDOT) and flat panel detector-based microcomputed tomography (micro-CT) to simultaneously reveal molecular and structural information in small animals. In fDOT, a 748 nm diode laser was used as an excitation source, while a cooled charge coupled device camera was adopted to collect transmission fluorescence. In micro-CT, a flat panel detector based on amorphous silicon, with active area of 13×13 cm2, and a microfocus x-ray tube were used. The fDOT system was mounted orthogonally to the micro-CT and the projection images were acquired without rotation of the sample, which is different from the method used for micro-CT alone. Both the finite element method and the algebraic reconstruction technique were used to reconstruct images from the fDOT. Phantom data showed that the resolution of the fDOT system was about 3 mm at an imaging depth of 7 mm. Quantitative error was no more than 5% and imaging sensitivity for 1,1′-d...

High resolution in vivo micro-CT with flat panel detector based on amorphous silicon.

Abstract: A high-resolution in vivo micro-CT system for combining with fluorescence molecular tomography (FMT), was constructed and applied in small animal imaging. The fast scanning micro-CT system designed to provide high-resolution anatomic information and reconstruction priors, consisted of a flat panel detector (FPD) based on amorphous silicon (a-Si) and a micro-focus x-ray tube. The Feldkamp algorithm was adopted in image reconstruction with graphic processing unit (GPU). The system spatial resolution of 13 lp/mm was achieved when the diameter of image field was 6 cm with the system magnification factor of 4. No obvious beam hardening artifact was observed in transaxial image of a water phantom after correction. The contrast-to-noise ratio (CNR) study of various tissue phantoms was also presented. The in-vivo imaging of an anesthetic mouse was performed to demonstrate the feasibility of our system.

High-resolution photoacoustic microscope for rat brain imaging in vivo

Abstract: A reflection-mode photoacoustic microscope (PAM) for rat brain imaging in vivo is constructed. A pulsed laser is used as an excitation source, and a focused ultrasound transducer is adopted to collect the photoacoustic signal. Raster scanning is applied to acquire three-dimensional (3D) data. The obtained measurements of the lateral and axial resolutions of the microscope are 45 and 15 \mu m, respectively. The imaging depth in the chicken breast tissue is 3.1 mm at a signal-to-noise ratio (SNR) of 20 dB without any signal averaging. The imaging speed is 30 A-line/s. Experimental results in vivo demonstrate the capability of 3D imaging of the brain vessels of the rat after removing the skull.

A ligation-independent cloning method using nicking DNA endonuclease

Abstract: Using nicking DNA endonuclease (NiDE), we developed a novel technique to clone DNA fragments into plasmids. We created a NiDE cassette consisting of two inverted NiDE substrate sites sandwiching an asymmetric four-base sequence, and NiDE cleavage resulted in 14-base single-stranded termini at both ends of the vector and insert. This method can therefore be used as a ligation-independent cloning strategy to generate recombinant constructs rapidly. In addition, we designed and constructed a simple and specific vector from an Escherichia coli plasmid back-bone to complement this cloning method. By cloning cDNAs into this modified vector, we confirmed the predicted feasibility and applicability of this cloning method.

Special method to prepare quantum dot probes with reduced cytotoxicity and increased optical property.

Abstract: Quantum dots (QDs) are widely used in the life sciences because of their novel physicochemical properties. However, the cytotoxity of these nonoparticles have attracted great attention recently because this has not been well resolved. Four probes were synthesized by chemical coupling and protein denaturation with CdSe/ZnS, CdTe QDs, and transferrin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and capillary electrophoresis were used to verify the conjugation of these luminescent probes. The cytotoxicity of these four luminescent probes and the original QDs were evaluated in HeLa cells. The results showed that over 92% of HeLa cells were still alive after being exposed to 3.2-µM CdSe/ZnS QDs capped with denatured transferrin for 72 h. Furthermore, while the probe preparation was very simple, the photoluminescence quantum yield of this probe was 7% higher than the original CdSe/ZnS QDs. This provides a new way for exploiting QD probes with low cytotoxicity, which will expand applications of nanocomposite assembly in biolabeling and imaging.

Characteristics of calcium signaling in astrocytes induced by photostimulation with femtosecond laser.

Abstract: Astrocytes have been identified to actively contribute to brain functions through Ca(2+) signaling, serving as a bridge to communicate with neurons and other brain cells. However, conventional stimulation techniques are hard to apply to delicate investigations on astrocytes. Our group previously reported photostimulation with a femtosecond laser to evoke astrocytic calcium (Ca(2+)) waves, providing a noninvasive and efficient approach with highly precise targeting. In this work, detailed characteristics of astrocytic Ca(2+) signaling induced by photostimulation are presented. In a purified astrocytic culture, after the illumination of a femtosecond laser onto one cell, a Ca(2+) wave throughout the network with reduced speed is induced, and intracellular Ca(2+) oscillations are observed. The intercellular propagation is pharmacologically confirmed to be mainly mediated by ATP through P(2)Y receptors. Different patterns of Ca(2+) elevations with increased amplitude in the stimulated astrocyte are discovered by varying the femtosecond laser power, which is correspondingly followed by broader intercellular waves. These indicate that the strength of photogenerated Ca(2+) signaling in astrocytes has a positive relationship with the stimulating laser power. Therefore, distinct Ca(2+) signaling is feasibly available for specific studies on astrocytes by employing precisely controlled photostimulation.

Transient alterations in slow oscillations of hippocampal networks by low-frequency stimulations on multi-electrode arrays

Abstract: Slow oscillations in the hippocampus are correlated with memory consolidation and brain diseases. The characteristic firings of the hippocampal network in vitro are still poorly understood. Here, spontaneous oscillations (~0.004 Hz) were found in high-density hippocampal networks by multi-electrode arrays after 30 days in vitro. This kind of spontaneous activity was characterized by periodic synchronized superbursts, which persisted for approximately 60 s at long intervals. Additionally, 1-Hz stimulation (duration <120 s) could regulate these network-wide oscillatory activities by triggering the next synchronized superbursts prematurely. The results demonstrated that the slow oscillatory activities in hippocampal cultures could be regulated by external stimulation, which indicates that multi-electrode arrays provide a well-suited platform for studying the dynamics of slow oscillations in vitro and may help to elucidate the mechanism of electrical stimulation therapy.

Investigating the effects of dimethylsulfoxide on hemodynamics during cortical spreading depression by combining laser speckle imaging with optical intrinsic signal imaging.

Abstract: Background and Objectives Cortical spreading depression (CSD) is an important pathological model to study cerebral ischemia and migraine. In pharmacological studies of CSD, dimethylsulfoxide (DMSO) is an efficient solvent for water-insoluble drugs. Previous studies indicated that DMSO could prevent pial arteriolar dilation induced by oxidants. Therefore, it was very important to study the effect of DMSO on hemodynamics during CSD so that optimization of dose of DMSO as solvent can be made. Study Design/Materials and Methods DMSO was topically applied on the exposed rat cortex. Single CSD was elicited by controlled injection of KCl. Pial arteriolar diameter, cerebral blood flow, and direct current potential during CSD were monitored by optical intrinsic signal imaging, laser speckle imaging, and electrophysiology method, respectively. Results Topical application of DMSO (0.1%, 0.4%, 2%, and 4%, v/v) increased arteriolar resting diameter and resting blood velocity at all vascular compartments. In addition, both vasodilation and hyperemic response to CSD were attenuated by DMSO in a dose-dependent manner at doses from 0.1% to 4%. In contrast, the maximum value of blood velocity during CSD was not significantly affected by DMSO. Conclusion The attenuation in hemodynamic response during CSD could possibly be caused by increased baseline value of vessel tone and blood velocity. Our findings suggest that when investigators use DMSO to dissolve water-insoluble, topically applied drugs in the hemodynamic study of CSD, dose of DMSO should be kept below 0.1% in order to avoid false results. Lasers Surg. Med. 42:809–815, 2010 © 2010 Wiley-Liss, Inc.

Spatial-temporal dynamics of chaotic behavior in cultured hippocampal networks.

Abstract: Using multiple nonlinear techniques, we revealed the existence of chaos in the spontaneous activity of neuronal networks in vitro. The spatial-temporal dynamics of these networks indicated that emergent transition between chaotic behavior and superburst occurred periodically in low-frequency oscillations. An analysis of network-wide activity indicated that chaos was synchronized among different sites. Moreover, we found that the degree of chaos increased as the number of active sites in the network increased during long-term development (over three months in vitro). The chaotic behavior of the dissociated networks had similar spatial-temporal characteristics (rapid transition, periodicity, and synchronization) as the intact brain; however, the degree of chaos depended on the number of active sites at the mesoscopic level. This work could provide insight into neural coding and neurocybernetics.

Portable laser speckle perfusion imaging system based on digital signal processor.

Abstract: The ability to monitor blood flow in vivo is of major importance in clinical diagnosis and in basic researches of life science. As a noninvasive full-field technique without the need of scanning, laser speckle contrast imaging (LSCI) is widely used to study blood flow with high spatial and temporal resolution. Current LSCI systems are based on personal computers for image processing with large size, which potentially limit the widespread clinical utility. The need for portable laser speckle contrast imaging system that does not compromise processing efficiency is crucial in clinical diagnosis. However, the processing of laser speckle contrast images is time-consuming due to the heavy calculation for enormous high-resolution image data. To address this problem, a portable laser speckle perfusion imaging system based on digital signal processor (DSP) and the algorithm which is suitable for DSP is described. With highly integrated DSP and the algorithm, we have markedly reduced the size and weight of the system as well as its energy consumption while preserving the high processing speed. In vivo experiments demonstrate that our portable laser speckle perfusion imaging system can obtain blood flow images at 25 frames per second with the resolution of 640 × 480 pixels. The portable and lightweight features make it capable of being adapted to a wide variety of application areas such as research laboratory, operating room, ambulance, and even disaster site.

Accurately determining propagation velocity of cortical spreading depression in rats by optical intrinsic signal imaging

Abstract: Cortical spreading depression (CSD) is a wave of neuronal and glial depolarization that propagates across the cortex at a rate of 2–5 mm/min accompanied by reversible electroencephalogram (EEG) suppression, a negative shift of direct current (DC) potential, and change of optical intrinsic signals (OIS). Propagation velocity of CSD is an important parameter used to study this phenomenon. It is commonly determined in an electrophysiological way that measures the time required for a CSD wave to pass along two electrodes. Since the electrophysiology technique fails to reveal the spreading pattern of CSD, velocity calculated in this manner might be inaccurate. In this study, we combined the electrophysiological recording and OIS imaging (OISI) for detecting changes in DC potential and OIS during CSD simultaneously. An optical method based on OISI to determine the CSD velocity, which is measured by generating a series of regions of interest (ROI) perpendicular to the advancing wavefront along propagation direct...

High speed parallel processing of biomedical optics data with PC graphic hardware

Abstract: In the field of biomedical optics, many approaches need to process tremendous data set using complicated algorithms, which cause heavy computation and limit their applications in the real-time conditions, such as clinical diagnoses and therapy. In this paper, we present and review several successful applications using GPU (graphic processing unit) to accelerate the processing of biomedical optics data including image processing, Monte Carlo simulation, image reconstruction and statistics analysis. It is shown that GPU are proved to obtain significant performance improvement in contrast with the traditional used methods based on CPU calculation.

ModuleNet: An R package on regulatory network building

Abstract: Many researchers have used microarray gene expression data to investigate gene regulatory networks in specific life stages. In these analyses, Bayesian network was widely applied to regulatory network building from expression profiles because of its solid mathematical foundation and its robust analysis ability in noisy data. However, the building of Bayesian network is time consuming and the searching space is really large. Considering the biological feature of transcription factors (TFs) and targets (TGs), the regulatory network is possible to be separated into core TFs networks and the interactions from TFs to TGs. We developed an R package named ModuleNet which used Bayesian network model to the inner TFs network building and genetic algorithm on TF-TG interactions prediction. With determined number of transcription factors, the searching space and time requirements of ModuleNet is linear increasing according to the number of targets. After application to yeast cell-cycle expression profile, the results demonstrated the prediction accuracy of ModuleNet. Furthermore, significantly enriched Gene Ontology (GO) terms with similar expression behaviors were detected automatically by ModuleNet from expression profile, and the relationships from TFs to GO terms were figured out. The source code is available by asking for the author.

Repeat burst for timing code in excitatory neuronal network on multi-electrode array

Abstract: Concise coding for input plays an important role in neural signal processing. In previous studies, three types of neural signal coding were raised: rate, timing and population coding. By multi-electrode array, the coding of input intensities in cultured hippocampal neuronal networks was examined. In excitatory neuronal network, responses to input intensities focused on the three periods: 1∼10 ms, 11∼30 ms, 41∼60 ms. The dynamics on firing rate to input intensities in each timings was distinct: in 1∼10 ms, the sublinear relationship to increasing input intensities was exhibited over the whole input range; in 11∼30 ms, only a transition was occurred in inputs from 300 to 400mV; in 41∼60 ms, a linear increase with input from 300 to 600 mV. These results suggest that the coding to input intensities was a complex mode that is repeat burst based-on timing in high density cultured neuronal network.

Effects of naag and mpep on rat cortical spreading depression

Abstract: Cortical spreading depression (CSD) is a pathophysiological phenomenon. There are sufficient evidences to prove that CSD plays an important role in some neurological disorders. However, exact mechanisms of its initiation and propagation are still unclear. Previous studies showed that glutamate receptors could be concerned with CSD, but those studies were mostly performed oriented to ionotropic glutamate receptors (iGluRs). There is relatively little report about effects of metabotropic glutamate receptors (mGluRs) on CSD. Here, we applied optical intrinsic signal imaging (OISI) combined with direct current (DC) potential recording to examine influences of some mGluRs antagonist (or agonist) on CSD propagation in rat's brain, to indirectly validate actions of some mGluRs on CSD. We found that N-acetyl-L-aspartyl-L-glutamate (NAAG, an agonist at mGluR3) inhibited the propagation of CSD, and the inhibition was gradually developed with time. However, 6-methyl-2-phenylethynyl-pyridine (MPEP, an antagonist of mGluR5) did not produce any significant alterations with the CSD propagation. Our findings suggest that mGluR3 could play an important role in the CSD propagation, but the activity of mGluR5 was comparatively weak. These findings can help to understand the propagation mechanism of CSD, and consider the therapy of some neurological diseases involved with CSD.

Mechanism for tissue optical clearing: physical and physiological research

Abstract: The optical clearing technique is able improve light penetration depth by applying optical clearing agent (OCA) with high refractive indices and hyperosmolarity. However, the mechanism of tissue optical clearing is not much clear. In this work, both physical and physiological mechanisms of optical clearing are discussed. For physical mechanisms, a tissue phantom, Intralipid, was mixed with OCAs, and then the reduced scattering coefficient was theoretically predicted and experimentally measured. It was found that the physical mechanisms for optical clearing are due to the structure change of scatters or the enhancement of the background refractive index. For physiological mechanisms, the dehydration of porcine skin in vitro caused by topical application of OCA was investigated with NIR reflectance spectrum analysis. The results showed that dehydration is major factor during the initial few minutes, and some other changes of tissue structure maybe occurs with increase of time. And the microstructure and ultrastructure of rat skin was examined after in vivo application of glycerol, we found that both the thickness of skin and the size of fiber reduce. This work is helpful for clarifying the mechanisms of tissue optical clearing, which will contribute to the improvement and clinical application of optical clearing technique.

Optical Sensors and Biophotonics II

Abstract: Editors 8–12 December 2010 Shanghai, China Cosponsored by IEEE Photonics Society • Optical Society of America • SPIE • Chinese Optical Society China Institute of Communications Local Organizing Committee Fudan University • Pudong Optoelectronics Industry Association of Shanghai Shanghai Jiao Tong University • Shanghai Institute of Optics and Fine Mechanics Alcatel-Lucent Shanghai Bell Best Student Paper Sponsor Thorlabs, Inc. Published by SPIE • Optical Society of Am erica • IEEE Photonics Society