Characterization of the angular memory effect of dynamic turbid media.

The optical angular memory effect (AME) is a basic feature of turbid media and defines the correlation of speckles when the incident light is tilted. AME based imaging through solid scattering media such as ground glass and biomedical tissue has been recently developed. However, in the case of liquid media such as turbid water or blood, the speckle pattern exhibits dynamic time-varying characteristics, which introduces several challenges. The AME of the thick volume dynamic media is particularly different from the layer scatterers. In practice, there are more parameters, e.g., scattering particle size, shape, density, or even the illuminating beam aperture that can influence the AME range. Experimental demonstration of AME phenomenon in liquid dynamic media and confirm the distinctions will contribution to complete the AME theory. In this paper, a dual-polarization speckle detection setup was developed to characterize the AME of dynamic turbid media, where two orthogonal polarized beams were employed for simultaneous detection by a single CCD. The AME of turbid water, milk and blood were measured. The influence of thickness, concentration, particle size and shape, and beam diameter were analyzed. The AME increasement of upon the decrease of beam diameter was tested and verified. The results demonstrate the feasibility of this method for investigating the AME phenomenon and provide guidance for AME based imaging through scattering media.

Low-dose dexamethasone promotes osteoblast viability by activating autophagy via the SGK1/FOXO3a signaling pathway.

Autophagy contributes to bone homeostasis and development under physiological conditions. Although previous studies have demonstrated the induction of the autophagy machinery by endogenous glucocorticoids (GCs), the precise mechanisms involved have not yet been clarified. The current study aimed to explore the effect of a low dose of GC (10-8 M dexamethasone, Dex) on autophagy in mouse embryonic osteoblastic precursor cells (MC3T3-E1 cells) and the potential mechanisms. The results showed that 10-8 M Dex induced significant time-dependent increases in the expression and activation of serum- and glucocorticoid-induced kinase-1 (SGK1) in MC3T3-E1 cells and that these effects were accompanied by increased cell viability and decreased apoptosis. The autophagy inhibitor 3-MA significantly inhibited Dex-mediated promotion of viability. Moreover, Dex increased LC3II and Beclin-1 levels and decreased SQSTM/p62 levels in a time-dependent manner, and these effects were attenuated by pretreatment with 3-MA. Transfection of Dex-treated MC3T3-E1 cells with shRNA-SGK1 resulted in a significant reduction in cell viability and an increase in apoptosis. 3-MA further exacerbated these effects of SGK1 inhibition. Knocking down SGK1 before Dex exposure significantly reduced the phosphorylated forkhead box O3a (p-FOXO3a)/FOXO3 ratio, suppressed LC3II and Beclin-1 levels, and increased SQSTM/p62 levels in MC3T3-E1 cells, and these effects were amplified by 3-MA. In conclusion, the results revealed that low-dose GC treatment increased osteoblast viability by activating autophagy via the SGK1/FOXO3a pathway.

Artemisinin suppressed tumour growth and induced vascular normalisation in oral squamous cell carcinoma via inhibition of macrophage migration inhibitory factor.

BACKGROUND: Tumour vascular normalisation therapy advocates a balance between pro-angiogenic factors and anti-angiogenic factors in tumours. Artemisinin (ART), which is derived from traditional Chinese medicine, has been shown to inhibit tumour growth; however, the relationship between ART and tumour vascular normalisation in oral squamous cell carcinoma (OSCC) has not been previously reported. METHODS: Different concentrations(0 mg/kg, 25 mg/kg, 50 mg/kg, 100 mg/kg)of ART were used to treat the xenograft nude mice model of OSCC. The effects of ART on migration and proliferation of OSCC and human umbilical vein endothelial cells (HUVEC) cells were detected by scratch assay and CCK-8 assay. OSCC cells with macrophage migration inhibitory factor (MIF) silenced were constructed to explore the effect of MIF. RESULTS: Treatment with ART inhibited the growth and angiogenesis of OSCC xenografts in nude mice and downregulated vascular endothelial growth factor (VEGF), IL-8, and MIF expression levels. ART reduced the proliferation, migration, and tube formation of HUVEC, as well as the expression of VEGFR1 and VEGFR2. When the dose of ART was 50 mg/kg, vascular normalisation of OSCC xenografts was induced. Moreover, VEGF and IL-8 were needed in rhMIF restoring tumour growth and inhibit vascular normalisation after the addition of rhMIF to ART-treated cells. CONCLUSION: Artemisinin might induce vascular normalisation and inhibit tumour growth in OSCC through the MIF-signalling pathway.

CXCL12/CXCR4 facilitates perineural invasion via induction of the Twist/S100A4 axis in salivary adenoid cystic carcinoma.

The activation of CXCL12/CXCR4 axis participated in the progression of multiple cancers, but potential effect in terms of perineural invasion (PNI) in SACC remained ambiguous. In this study, we identified that CXCL12 substantially expressed in nerve cells. CXCR4 strikingly expressed in tumour cells, and CXCR4 expression was closely associated with the level of EMT-associated proteins and Schwann cell hallmarks at nerve invasion frontier in SACC. Activation of CXCL12/CXCR4 axis could promote PNI and up-regulate relative genes of EMT and Schwann cell hallmarks both in vitro and in vivo, which could be inhibited by Twist silence. After overexpressing S100A4, the impaired PNI ability of SACC cells induced by Twist knockdown was significantly reversed, and pseudo foot was visualized frequently. Collectively, the results indicated that CXCL12/CXCR4 might promote PNI by provoking the tumour cell to differentiate towards Schwann-like cell through Twist/S100A4 axis in SACC.

Extended field of view of light-sheet fluorescence microscopy by scanning multiple focus-shifted Gaussian beam arrays.

Light-sheet fluorescence microscopy (LSFM) facilitates high temporal-spatial resolution, low photobleaching and phototoxicity for long-term volumetric imaging. However, when a high axial resolution or optical sectioning capability is required, the field of view (FOV) is limited. Here, we propose to generate a large FOV of light-sheet by scanning multiple focus-shifted Gaussian beam arrays (MGBA) while keeping the high axial resolution. The positions of the beam waists of the multiple Gaussian beam arrays are shifted in both axial and lateral directions in an optimized arranged pattern, and then scanned along the direction perpendicular to the propagation axis to form an extended FOV of light-sheet. Complementary beam subtraction method is also adopted to further improve axial resolution. Compared with the single Gaussian light-sheet method, the proposed method extends the FOV from 12 µm to 200 µm while sustaining the axial resolution of 0.73 µm. Both numerical simulation and experiment on samples are performed to verify the effectiveness of the method.

Axial resolution enhancement for planar Airy beam light-sheet microscopy via the complementary beam subtraction method.

Airy beam light-sheet illumination can extend the field of view (FOV) of light-sheet fluorescence microscopy due to the unique propagation properties of non-diffraction and self-acceleration. However, the side lobes create undesirable out-of-focus background, leading to poor axial resolution and low image contrast. Here, we propose an Airy complementary beam subtraction (ACBS) method to improve the axial resolution while keeping the extended FOV. By scanning the optimized designed complementary beam that has two main lobes (TML), the generated complementary light-sheet has almost identical intensity distribution to that of the planar Airy light-sheet except for the central lobe. Subtraction of the two images acquired by double exposure respectively using the planar Airy light-sheet and the planar TML light-sheet can effectively suppress the influence of the out-of-focus background. The axial resolution improves from ∼4µm to 1.2 µm. The imaging performance was demonstrated by imaging specimens of aspergillus conidiophores and GFP labeled mouse brain section. The results show that the ACBS method enables the Airy beam light-sheet fluorescence microscopy to obtain better imaging quality.

Fatty acid synthase contributes to epithelial-mesenchymal transition and invasion of salivary adenoid cystic carcinoma through PRRX1/Wnt/ß-catenin pathway.

Fatty acid synthase (FASN) has been shown to be selectively up-regulated in cancer cells to drive the development of cancer. However, the role and associated mechanism of FASN in regulating the malignant progression of salivary adenoid cystic carcinoma (SACC) still remains unclear. In this study, we demonstrated that FASN inhibition attenuated invasion, metastasis and EMT of SACC cells as well as the expression ofPRRX1, ZEB1, Twist, Slug and Snail, among which the level of PRRX1 changed the most obviously. Overexpression of PRRX1 restored migration and invasion in FASN knockdown cells, indicating that PRRX1 is an important downstream target of FASN signalling. Levels of cyclin D1 and c-Myc, targets of Wnt/ß-catenin pathway, were significantly decreased by FASN silencing and restored by PRRX1 overexpression. In addition, FASN expression was positively associated with metastasis and poor prognosis of SACC patients as well as with the expression of PRRX1, cyclin D1 and c-Myc in SACC tissues. Our findings revealed that FASN in SACC progression may induce EMT in a PRRX1/Wnt/ß-catenin dependent manner.

Rapid tilted-plane Gerchberg-Saxton algorithm for holographic optical tweezers.

Benefitting from the development of commercial spatial light modulator (SLM), holographic optical tweezers (HOT) have emerged as a powerful tool for life science, material science and particle physics. The calculation of computer-generated holograms (CGH) for generating multi-focus arrays plays a key role in HOT for trapping of a bunch of particles in parallel. To realize dynamic 3D manipulation, we propose a new tilted-plane GS algorithm for fast generation of multiple foci. The multi-focal spots with a uniformity of 99% can be generated in a tilted plane. The computation time for a CGH with 512×512 pixels is less than 0.1 second. We demonstrated the power of the algorithm by simultaneously trapping and rotating silica beads with a 7×7 spots array in three dimensions. The presented algorithm is expected as a powerful kernel of HOT.

Polarization-dependent micro-structure fabrication with direct femtosecond laser writing on plastic polarizer films.

Iodine-doped polyvinyl alcohol (IDPVA) film has been widely used as a plastic polarizer due to its great linear dichroism. We found that the anisotropic character of the plastic polarizer can be permanently damaged upon exposure of high intensity femtosecond laser pulses. This process is a two-photon-induced chemical reaction and denominated as two-photon-induced isotropy (TPII). The TPII effect can form a high polarization contrast on the base of the original IDPVA films. With this property, polarization-sensitive diffractive optical elements are fabricated in IDPVA films. The low cost of the IDPVA film and the high polarization contrast of TPII make it a promising new candidate for femtosecond laser fabrication of polarization-selective optical elements.

Full-polarization wavefront shaping for imaging through scattering media.

The scattering effect occurring when light passes through inhomogeneous-refractive-index media such as atmosphere or biological tissues will scramble the light wavefront into speckles and impede optical imaging. Wavefront shaping is an emerging technique for imaging through scattering media that works by addressing correction of the disturbed wavefront. In addition to the phase and amplitude, the polarization of the output scattered light will also become spatially randomized in some cases. The recovered image quality and fidelity benefit from correcting as much distortion of the scattered light as possible. Liquid-crystal spatial light modulators (LC-SLMs) are widely used in the wavefront shaping technique, since they can provide a great number of controlled modes and thereby high-precision wavefront correction. However, due to the working principle of LC-SLMs, the wavefront correction is restricted to only one certain linear polarization state, resulting in retrieved image information in only the right polarization, while the information in the orthogonal polarization is lost. In this paper, we describe a full-polarization wavefront correction system for shaping the scattered light wavefront in two orthogonal polarizations with a single LC-SLM. The light speckles in both polarizations are corrected for retrieval of the full polarization information and faithful images of objects. As demonstrated in the experiments, the focusing intensity can be increased by full-polarization wavefront correction, images of objects in arbitrary polarization states can be retrieved, and the polarization state of the object's light can also be recognized.

MIF promotes perineural invasion through EMT in salivary adenoid cystic carcinoma.

Macrophage migration inhibitory factor (MIF) is a prominent orchestrator during the onset and progression of cancer. Recently, MIF was detected in salivary adenoid cystic carcinoma (SACC). However, its functional effect in perineural invasion (PNI) of SACC remained unknown. To illuminate the effect of MIF in genesis of PNI in SACC, we examined the expression of MIF, epithelial-to-mesenchymal transition (EMT)-related markers, and Schwann cell markers by immunohistochemical analysis in 158 cases of SACC samples. Meanwhile, the correlation between MIF and PNI of SACC species was analyzed. Our data indicated that MIF expression was associated with PNI of SACC significantly. In vitro, the silence and overexpression experiments of MIF were performed in SACC cell lines. The ability of migration, invasion and PNI could be inhibited significantly by siRNA-mediated MIF silence, and the occurrence of EMT and Schwann-like cell differentiation was also inhibited by MIF silence in SACC-LM cells. Overexpression of MIF in SACC-83 cells using expressive plasmid showed the opposite effects. Our findings identified that an association between PNI and MIF expression existed. MIF may promote PNI of SACC by participating in cytoskeletal reorganization and pseudo foot formation induced by EMT and the Schwann-like cell differentiation of SACC cells.

Macrophage migration inhibitory factor promotes the invasion and metastasis of oral squamous cell carcinoma through matrix metalloprotein-2/9.

Macrophage migration inhibitory factor (MIF) has been shown to closely associate with the malignant progression of a variety of human carcinomas. However, the role and its underlying molecular mechanisms of MIF in the invasion and metastasis of oral squamous cell carcinoma (OSCC) still remains unclear. Here, we found that MIF silencing reduced the cell proliferation, migration, and invasion, as well as matrix metalloprotein-2 (MMP-2) and MMP-9 in OSCC cells. Overexpression of MMP-2 or MMP-9 restored the migration and invasion of MIF-knockdown cells, indicating that MMP-2 and MMP-9 are downstream targets of MIF. In the xenograft model, MIF silencing inhibited tumor growth and in lymph metastasis model, MIF silencing reduced tumor metastasis. More importantly, immunohistochemistry staining in a tissue microarray (TMA) demonstrated that MIF expression was positively correlated with clinic stage, recurrence, metastasis, and poor prognosis of patients with OSCC as well as with the levels of MMP-2 or MMP-9 in TMA. Therefore, our findings suggest that MIF may promote the invasion and metastasis of OSCC through the activation of MMP-2 and MMP-9 and prompt further investigation into the therapeutic value of MIF for OSCC treatment.

Real-time optical manipulation of particles through turbid media.

Complex diffusive scattering media pose significant challenges for light focusing as well as optical imaging to be implemented in practice. Recently, it has been demonstrated that the wavefront shaping technique can be applied to realize focusing and imaging through scattering medium. Here we report dynamic optical manipulation of particles through turbid media by employing the interleaved segment wavefront correction method, which is an improved genetic algorithm providing faster convergence speed and higher peak to background ratio. Manipulating micro-beads behind a scattering medium along both one and two dimensional predesigned trajectories in real time has been successfully demonstrated.

Robust contrast-transfer-function phase retrieval via flexible deep learning networks: publisher's note.

This publisher's note contains corrections to Opt. Lett.44, 5141 (2019)OPLEDP0146-959210.1364/OL.44.005141.

Robust contrast-transfer-function phase retrieval via flexible deep learning networks.

By exploiting the total variation (TV) regularization scheme and the contrast transfer function (CTF), a phase map can be retrieved from single-distance coherent diffraction images via the sparsity of the investigated object. However, the CTF-TV phase retrieval algorithm often struggles in the presence of strong noise, since it is based on the traditional compressive sensing optimization problem. Here, convolutional neural networks, a powerful tool from machine learning, are used to regularize the CTF-based phase retrieval problems and improve the recovery performance. This proposed method, the CTF-Deep phase retrieval algorithm, was tested both via simulations and experiments. The results show that it is robust to noise and fast enough for high-resolution applications, such as in optical, x-ray, or terahertz imaging.

NR2F1 contributes to cancer cell dormancy, invasion and metastasis of salivary adenoid cystic carcinoma by activating CXCL12/CXCR4 pathway.

BACKGROUND: Salivary adenoid cystic carcinoma (SACC) can recur after removal of the primary tumor and treatment, where they can keep no clinical symptoms and dormant state for 10-15 years. NR2F1 has been demonstrated to regulate the tumor cell dormancy in various malignant tumors and has a potential impact on recurrence and metastasis of carcinoma. However, the role and significance of NR2F1 in SACC dormancy still remain unknown. METHODS: A total number of 59 patients with a diagnosis of SACC were included to detected expression of NR2F1, Ki-67 by immunohistochemical (IHC) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick and labeling (TUNEL). Fisher's exact test was used to examine the NR2F1 expression and clinicopathologic parameters of SACC. In vitro, SACC cell lines were transfected NR2F1 and knockdown NR2F1 respectively. CCK-8, flow cytometry, wound healing assay and transwell invasion determined SACC cell proliferation, apoptosis, cell cycle, migration and invasion respectively. Chromatin immunoprecipitation (ChIP) assays were utilized to demonstrate the potential role of NR2F1 in SACC invasion via CXCL12/CXCR4 axis. In vivo, xenografts of nude mice via subcutaneous injection or tail vein injection were used to testify the results in vitro. RESULTS: Among the 59 patients with SACC, 23.73% (14/59) were positive to NR2F1 expression, a lower rate of expression compared with 60% (6/10) in normal salivary gland samples. NR2F1 was correlated with metastasis, relapse and dormancy of SACC. SACC cells with transfected NR2F1 remained dormant, as well as enhanced invasion and metastasis. Knockdown of NR2F1 via siRNA after NR2F1 overexpression restored the proliferation and the cell number in G2/M phases, and reduced the abilities of migration and invasion. In addition, NR2F1 promoted the expression of CXCL12 and CXCR4, and overexpression of CXCL12 at least partly rescued the proliferation, migration, and invasion activities induced by NR2F1 silencing. CONCLUSIONS: NR2F1 may be an underlying mechanism of SACC recurrence and metastasis via regulating tumor cell dormancy through CXCL12/CXCR4 pathway.

Rapid wide-field imaging through scattering media by digital holographic wavefront correction.

Imaging through scattering media has been a long standing challenge in many disciplines. One of the promising solutions to address the challenge is the wavefront shaping technique, in which the phase distortion due to a scattering medium is corrected by a phase modulation device such as a spatial light modulator (SLM). However, the wide-field imaging speed is limited either by the feedback-based optimization to search the correction phase or by the update rate of SLMs. In this report, we introduce a new method called digital holographic wavefront correction, in which the correction phase is determined by a single-shot off-axis holography. The correction phase establishes the so-called "scattering lens", which allows any objects to be imaged through scattering media; in our case, the "scattering lens" is a digital one established through computational methods. As no SLM is involved in the imaging process, the imaging speed is significantly improved. We have demonstrated that moving objects behind scattering media can be recorded at the speed of 2.8 fps with each frame corrected by the updated correction phase while the image contrast is maintained as high as 0.9. The image speed can potentially reach the video rate if the computing power is sufficiently high. We have also demonstrated that the digital wavefront correction method also works when the light intensity is low, which implicates its potential usefulness in imaging dynamic processes in biological tissues.

Optical thickness measurement with single-shot dual-wavelength in-line digital holography.

An algorithm for quantitative reconstruction of the optical thickness distribution of objects is proposed based on single-shot dual-wavelength in-line digital holography. Two single-wavelength holograms can be extracted from a single-shot recorded dual-wavelength in-line hologram. The quantitative optical thickness distribution of the specimen can be reconstructed directly without calculations of the phase images at every single wavelength. Thus, off-axis recording and phase-shifting operation are not required, enabling a fast and high-resolution measurement. The effectiveness and accuracy of the proposed method are verified by both numerical simulations and experimental results.

Polypyrrole Nanotube-Derived Carbon Aerogels as Efficient and Recyclable Oil Absorbents.

Polypyrrole nanotube-derived carbon aerogels with three-dimensional networks have been prepared via freeze-drying and pyrolysis method using polypyrrole nanotubes as precursors. The resulting carbon nanotube aerogels display ultra-low density, fairly high mechanical properties, water repellency, superoleophilicity, high absorption capacity and fast absorption rate of oil and organic solvents. Its absorption capacity can reach in the range from 140 to 600 times of its own weight for the utilized common oil and organic solvents. Furthermore, the carbon nanotube aerogels demonstrate outstanding recyclability by distill or direct combustion in air because of their excellent hydrophobicity and fire-resistant properties. Significantly, the carbon nanotube aerogels maintain 82.2% absorption capacity after 100 absorption/combustion cycles. Our results suggest that the polypyrrole nanotube-derived carbon aerogels are suitable absorbents for a wide range of applications in water environment protection.

Rotating of low-refractive-index microparticles with a quasi-perfect optical vortex.

Low-refractive-index microparticles, such as hollow microspheres, have shown great significance in some applications, such as biomedical sensing and targeted drug delivery. However, optical trapping and manipulation of low-refractive-index microparticles are challenging, owing to the repelling force exerted by typical optical traps. In this paper, we demonstrated optical trapping and rotating of large-sized low-refractive-index microparticles by using quasi-perfect optical vortex (quasi-POV) beams, which were generated by Fourier transform of high-order quasi-Bessel beams. Numerical simulation was carried out to characterize the focusing property of the quasi-POV beams. The dynamics of low-refractive-index microparticles in the quasi-POV with various topological charges was investigated in detail. To improve the trapping and rotating performances of the vortex, a point trap was introduced at the center of the ring. Experimental results showed that the quasi-POV was preferable for manipulation of large-sized low-refractive-index microparticles, with its control of the particles' rotating velocity dependent only on the topological charge due to the unchanged orbital radius.