3D high precision laser printing of a flat nanofocalizer for subwavelength light spot array.

Here, we demonstrate a flat nanofocalizer for converging light field into a uniform subwavelength light spot array based on the fractional Talbot effect by developing a direct laser writing technique with 3D fabrication precision. The fractional Talbot effect endows the device with the merits of high compression ratio and modular design capability for transforming a plane wave into arrayed light focal spots. By combining a synergistic laser printing technique, we introduce a buffer layer for improving the fabrication precision of structural height in favor of accurately manipulating the phase delay. For a given light wavelength at 750 nm, by precisely producing a nanofocalizer consisting of periodic unit elements with the dimensions of 300(width)×600(length)×585(height)nm, we have achieved 5×6 light spot array with modular design, while the full width at half-maximum of a single focused light spot can be reduced to ∼0.82λ. Our research may pave the way for realizing subwavelength optical devices capable of being readily integrated to existing optical systems.

Laser nanoprinting of floating three-dimensional plasmonic color in pH-responsive hydrogel.

Recent demonstrations of metasurfaces present their great potential to implement flat and multifunctional optical elements, which are accomplished with the designs of planar optics and micro-/nano- fabrications. Integrating metasurfaces in three dimensions has manifested drastically increasing advantages in manipulating light fields by extending design freedom. However, fabricating three-dimensional metasurfaces remain a tough challenge due to the lack of stereo printing protocols. Herein, we demonstrate laser nanoprinting of floated silver nanoparticle array in transparent hydrogel films for 3D metasurface to achieve color patterning. It is found that spatially resolved nanoparticles can be produced through laser induced photoreduction of silver ions and robustly anchored to the gel backbones by a focused femtosecond laser beam within a pH-responsive smart hydrogel matrix. With the aid of expansion properties of the pH-responsive hydrogel, repetitive coloration of the patterned plasmonic nanoparticle array over a wide spectrum range is achieved via reversible regulation of nanoparticle spacing from 550 to 350 nm and vice versa. This approach allows broadband 3D color-regulation in nanoscale for applications in active spectral filtering, information encryption, security tagging and biological colorimetric sensing, etc.

Planar chiral metasurfaces with maximal and tunable chiroptical response driven by bound states in the continuum.

Optical metasurfaces with high quality factors (Q-factors) of chiral resonances can boost substantially light-matter interaction for various applications of chiral response in ultrathin, active, and nonlinear metadevices. However, current approaches lack the flexibility to enhance and tune the chirality and Q-factor simultaneously. Here, we suggest a design of chiral metasurface supporting bound state in the continuum (BIC) and demonstrate experimentally chiroptical responses with ultra-high Q-factors and near-perfect circular dichroism (CD = 0.93) at optical frequencies. We employ the symmetry-reduced meta-atoms with high birefringence supporting winding elliptical eigenstate polarizations with opposite helicity. It provides a convenient way for achieving the maximal planar chirality tuned by either breaking in-plane structure symmetry or changing illumination angle. Beyond linear CD, we also achieved strong near-field enhancement CD and near-unitary nonlinear CD in the same planar chiral metasurface design with circular eigen-polarization. Sharply resonant chirality realized in planar metasurfaces promises various practical applications including chiral lasers and chiral nonlinear filters.

Antihypoxic effects of neuroglobin in hypoxia-preconditioned mice and SH-SY5Y cells.

This work aims at investigating the neuroprotective effects of neuroglobin (Ngb) in vivo and in vitro. RT-PCR and Western blotting were used to examine Ngb mRNA and protein levels in the mouse cortex after acute and repeated exposure to hypoxia. The cDNAs of mouse Ngb were cloned and transfected into SH-SY5Y cells to examine Ngb function in vitro. Expression of Ngb and mRNA was upregulated in the cortex of mice preconditioned by repetitive exposure to hypoxia. Tolerance to hypoxia of Ngb-transformed SH-SY5Y cells was enhanced. These results suggest that Ngb might be involved in hypoxic preconditioning which protects neurons from hypoxic injury.

Long-term changes in morphology, D2R expression and targets of regenerated dopaminergic terminals in the striatum after a partial lesion in the substantia nigra in the rat.

During Parkinson's disease (PD), compensatory regeneration or sprouting of fibers from surviving dopaminergic neurons in the striatum occurs in response to the lesion in the substantia nigra pars compacta (SNpc). The morphological characteristics of regenerated terminal have previously been shown to differ from normal terminals. Here, we provide insights into the morphological characteristics of regenerated dopaminergic terminals in the striatum over a 16-week period after a partial SNpc lesion. The dopaminergic fibers were almost completely lost in the dorsal part of the striatum 2weeks after the lesion, but returned to normal by 16weeks with an equal degree of dopaminergic neuron lesions in the SN at both time points. Morphologically, the regenerated dopaminergic terminals in the striatum were larger in size and had more small and large vesicles with a down-regulation of D(2) dopamine receptor (D(2)R). These terminals were more frequently in contact with D(2)R bearing neurons than D(1)R bearing neurons in the striatum. Therefore, the results indicate that dopaminergic fibers did regenerate in the dorsal part of the striatum after the SNpc lesion. Their morphological characteristics intuitively indicate that they were capable of delivering larger amounts of dopamine (DA) to compensate for the depletion, and to balance the secretion and re-uptake of DA after the lesion. The targeted change in regenerated dopaminergic terminals may disrupt the balance between the direct and indirect pathways in the basal ganglia, thereby resulting in the onset of PD symptoms.

Dopaminergic axons preferentially innervate dendritic spines with hyperactive glutamatergic synapses in the rat striatum.

Dopaminergic and glutamatergic afferents simultaneously innervate median spiny neurons (MSNs) and interact to mediate basal ganglia functions. However, the association between dopaminergic and glutamatergic axons is not clear. In the present study, nigrostriatal, corticostriatal, and thalamostriatal axons were anterogradely traced with biotinylated dextran amines (BDA) in rats, and MSNs were labeled with chloromethylbenzamido-DiI for neurogeometric analysis. Results showed that nigrostriatal, but not corticostriatal or thalamostriatal, axons were biased to a target on dendritic spines of the MSNs. In addition, the MSN dendritic spines, which were innervated by tyrosine hydroxylase-immunoreactive (TH-IR) axons and vesicular glutamate transporter 1 or 2-immunoreactive (VGluT-IR) terminals, were significantly larger than dendritic spines innervated by VGluT-IR terminals alone. Under electron microscopy, glutamatergic synapses on the dendritic spines were located with TH-IR terminals and displayed longer postsynaptic density. In addition, these synapses were more perforated than those on dendritic spines lacking innervated TH-IR terminals. These results demonstrated that dopaminergic axons were biased to a target and preferred to innervate dendritic spines with hyperactive and high-efficacy glutamatergic synapses in the striatum.