Prevalence of Two-Dimensional Photonic Topology.

Despite intense research in topological photonics for more than a decade, the basic question of whether photonic band topology is rare or abundant-i.e., its relative prevalence-remains open. Here, we use symmetry analysis and a dataset of 550 000 synthetic two-dimensional photonic crystals to determine the prevalence of stable, fragile, and higher-order topology across 11 plane groups and find a general abundance of nontrivial band topology. Below the first band gap and with time-reversal symmetry, stable topology is more prevalent in the transverse electric polarization, is weakly dependent on contrast, and fragile topology is nearly absent. In time-reversal broken settings, Chern insulating phases are also abundant, albeit less so in threefold symmetric settings. Our results elucidate the role of symmetry, dielectric contrast, polarization, and time-reversal breaking in engendering topological photonic phases and may inform new design principles for their experimental realization.

Weyl Points on Nonorientable Manifolds.

Weyl fermions are hypothetical chiral particles that can also manifest as excitations near three-dimensional band crossing points in lattice systems. These quasiparticles are subject to the Nielsen-Ninomiya "no-go" theorem when placed on a lattice, requiring the total chirality across the Brillouin zone to vanish. This constraint results from the topology of the (orientable) manifold on which they exist. Here, we ask to what extent the concepts of topology and chirality of Weyl points remain well defined when the underlying manifold is nonorientable. We show that the usual notion of chirality becomes ambiguous in this setting, allowing for systems with a nonzero total chirality. This circumvention of the Nielsen-Ninomiya theorem stems from a generic discontinuity of the vector field whose zeros are Weyl points. Furthermore, we discover that Weyl points on nonorientable manifolds carry an additional Z_{2} topological invariant which satisfies a different no-go theorem. We implement such Weyl points by imposing a nonsymmorphic symmetry in the momentum space of lattice models. Finally, we experimentally realize all aspects of their phenomenology in a photonic platform with synthetic momenta. Our work highlights the subtle but crucial interplay between the topology of quasiparticles and of their underlying manifold.

Polarization and Weak Topology in Chern Insulators.

Chern insulators, and more broadly, topological insulators, present an obstruction to the construction of exponentially localized electronic Wannier functions. This implies a fundamental difficulty in determining whether such insulators exhibit electric polarization. Here, we show that these insulators can indeed exhibit bound charges and adiabatic currents consistent with changes in bulk polarization over space and time, respectively. We also show that the change in polarization across crystalline domains within these strong topological insulators is quantized in the presence of crystalline symmetries.

Enhanced Skin Permeation of 5-Fluorouracil through Drug-in-Adhesive Topical Patches.

5-fluorouracil (5-FU), commercially available as a topical product, is approved for non-melanoma skin cancer (NMSC) treatment with several clinical limitations. This work aimed to develop 5-FU-loaded topical patches as a potential alternative to overcome such drawbacks. The patches offer accurate dosing, controlled drug release and improved patient compliance. Our study highlights the development of Eudragit® E (EuE)-based drug-in-adhesive (DIA) patches containing a clinically significant high level of 5-FU (approximately 450 µg/cm2) formulated with various chemical permeation enhancers. The patches containing Transcutol® (Patch-TRAN) or oleic acid (Patch-OA) demonstrated significantly higher skin penetration ex vivo than their control counterpart, reaching 5-FU concentrations of 76.39 ± 27.7 µg/cm2 and 82.56 ± 8.2 µg/cm2, respectively. Furthermore, the findings from in vitro permeation studies also validated the superior skin permeation of 5-FU achieved by Patch-OA and Patch-TRAN over 72 h. Moreover, the EuE-based DIA patch platform demonstrated suitable adhesive and mechanical properties with an excellent safety profile evaluated through an inaugural in vivo human study involving 11 healthy volunteers. In conclusion, the DIA patches could be a novel alternative option for NMSC as the patches effectively deliver 5-FU into the dermis layer and receptor compartment ex vivo for an extended period with excellent mechanical and safety profiles.

Development and Optimization of Imiquimod-Loaded Nanostructured Lipid Carriers Using a Hybrid Design of Experiments Approach.

Background: Imiquimod (IMQ) is an immunomodulating drug that is approved for the treatment of superficial basal cell carcinoma, actinic keratosis, external genital warts and perianal warts. However, IMQ cream (Aldara®) has several drawbacks including poor skin permeation, local toxicity, and compromised patient compliance as a topical pharmacological option. Methods: Our research aimed to develop and optimize nanostructured lipid carriers (NLCs) containing IMQ for the first time using a hybrid design of experiments approach. The optimized formulation was then incorporated into a matrix-type topical patch as an alternative dosage form for topical application and evaluated for IMQ deposition across different skin layers in comparison to the performance of the commercial product. Additionally, our work also attempted to highlight the possibility of implementing environment-friendly practices in our IMQ-NLCs formulation development by reviewing our analytical methods and experimental designs and reducing energy and solvent consumption where possible. Results: In this study, stearyl alcohol, oleic acid, Tween® 80 (polysorbate 80), and Gelucire® 50/13 (Stearoyl polyoxyl-32 glycerides) were selected for formulation development. The formulation was optimized using a 2k factorial design and a central composite design. The optimized formulation achieved the average particle size, polydispersity index, and zeta potential of 75.6 nm, 0.235, and - 30.9 mV, respectively. Subsequently, a matrix-type patch containing IMQ-NLCs was developed and achieved a statistically significant improvement in IMQ deposition in the deeper skin layers. The IMQ deposition from the patch into the dermis layer and receptor chamber was 3.3 ± 0.9 µg/cm2 and 12.3 ± 2.2 µg/cm2, while the commercial cream only deposited 1.0 ± 0.8 µg/cm2 and 1.5 ± 0.5 µg/cm2 of IMQ, respectively. Conclusion: In summary, IMQ-NLC-loaded patches represent great potential as a topical treatment option for skin cancer with improved patient compliance.

Effect of plasticizers on drug-in-adhesive patches containing 5-fluorouracil.

Topical patches containing 5-fluorouracil (5-FU) are a feasible alternative to overcome the shortcomings of commercial cream for the treatment of non-melanoma skin cancer (NMSC). Plasticizers are a critical component of drug-in-adhesive (DIA) patches as they can significantly affect the mechanical, adhesive and drug release characteristics of the patches. Eudragit® E (EuE) is a methacrylate-based cationic copolymer capable of producing flexible and adhesive films for topical application. In this study, the effect of plasticizers on the mechanical, adhesive and 5-FU release characteristics of EuE-based patches was comprehensively evaluated. While the elongation at break (%) and adhesion of the films were significantly increased with increasing triacetin, dibutyl sebacate (DBS) and triethyl citrate (TEC) concentrations, the tensile strength showed an inverse relationship. EuE plasticized with 40% triacetin, 30% DBS or 40% w/w TEC produced elastic and adhesive films most suitable for topical application. In vitro release studies of the 5-FU-loaded patches demonstrated an initial burst release pattern during the first 10 min followed by a slow release over 120 min. In summary, this study provides important information on effect of plasticizers for preparation of EuE-based patches with desired mechanical, adhesive and release characteristics of 5-FU towards their potential application in the treatment of NMSC.

Observation of bound states in the continuum embedded in symmetry bandgaps.

In the past decade, symmetry-protected bound states in the continuum (BICs) have proven to be an important design principle for creating and enhancing devices reliant upon states with high-quality (Q) factors, such as sensors, lasers, and those for harmonic generation. However, as we show, current implementations of symmetry-protected BICs in photonic crystal slabs can only be found at the center of the Brillouin zone and below the Bragg diffraction limit, which fundamentally restricts their use to single-frequency applications. By microprinting a three-dimensional (3D) photonic crystal structure using two-photon polymerization, we demonstrate that this limitation can be overcome by altering the radiative environment surrounding the slab to be a 3D photonic crystal. This allows for the protection of a line of BICs by embedding it in a symmetry bandgap of the crystal. This concept substantially expands the design freedom available for developing next-generation devices with high-Q states.

A Case of Eccrine Mucinous Carcinoma Involving Scalp.

The report presents a case of a 67-year-old female with a long-standing lump on the scalp. After its excision the histopathology revealed consistency with eccrine mucinous carcinoma. These neoplasms are quite rare with only around 100 cases reported since 1951. The report concludes the importance of encouraging follow-up of cutaneous lesions among patients as well as ongoing research to better identify and manage the tumor.

Point-Defect-Localized Bound States in the Continuum in Photonic Crystals and Structured Fibers.

We show that point defects in two-dimensional photonic crystals can support bound states in the continuum (BICs). The mechanism of confinement is a symmetry mismatch between the defect mode and the Bloch modes of the photonic crystal. These BICs occur in the absence of band gaps and therefore provide an alternative mechanism to confine light. Furthermore, we show that such BICs can propagate in a fiber geometry and exhibit arbitrarily small group velocity which could serve as a platform for enhancing nonlinear effects and light-matter interactions in structured fibers.

Pirfenidone-Induced Photosensitive Dermatitis: A Rare Side Effect.

Many classes of drugs are known to cause a photosensitive reaction, including anti-bacterial, anti-inflammatory, and nonsteroidal drugs. Pirfenidone is an anti-inflammatory drug that is used to treat idiopathic pulmonary fibrosis (IPF). We report a case of a patient who developed a photosensitive rash secondary to pirfenidone use, which resolved after discontinuing administration of the drug.

Observation of a Charge-2 Photonic Weyl Point in the Infrared.

Weyl points are robust point degeneracies in the band structure of a periodic material, which act as monopoles of Berry curvature. They have been at the forefront of research in three-dimensional topological materials as they are associated with novel behavior both in the bulk and on the surface. Here, we present the experimental observation of a charge-2 photonic Weyl point in a low-index-contrast photonic crystal fabricated by two-photon polymerization. The reflection spectrum obtained via Fourier-transform infrared spectroscopy closely matches simulations and shows two bands with quadratic dispersion around a point degeneracy.

Inhibitory Gating of Input Comparison in the CA1 Microcircuit.

Spatial and temporal features of synaptic inputs engage integration mechanisms on multiple scales, including presynaptic release sites, postsynaptic dendrites, and networks of inhibitory interneurons. Here we investigate how these mechanisms cooperate to filter synaptic input in hippocampal area CA1. Dendritic recordings from CA1 pyramidal neurons reveal that proximal inputs from CA3 as well as distal inputs from entorhinal cortex layer III (ECIII) sum sublinearly or linearly at low firing rates due to feedforward inhibition, but sum supralinearly at high firing rates due to synaptic facilitation, producing a high-pass filter. However, during ECIII and CA3 input comparison, supralinear dendritic integration is dynamically balanced by feedforward and feedback inhibition, resulting in suppression of dendritic complex spiking. We find that a particular subpopulation of CA1 interneurons expressing neuropeptide Y (NPY) contributes prominently to this dynamic filter by integrating both ECIII and CA3 input pathways and potently inhibiting CA1 pyramidal neuron dendrites.

Conjunctive input processing drives feature selectivity in hippocampal CA1 neurons.

Feature-selective firing allows networks to produce representations of the external and internal environments. Despite its importance, the mechanisms generating neuronal feature selectivity are incompletely understood. In many cortical microcircuits the integration of two functionally distinct inputs occurs nonlinearly through generation of active dendritic signals that drive burst firing and robust plasticity. To examine the role of this processing in feature selectivity, we recorded CA1 pyramidal neuron membrane potential and local field potential in mice running on a linear treadmill. We found that dendritic plateau potentials were produced by an interaction between properly timed input from entorhinal cortex and hippocampal CA3. These conjunctive signals positively modulated the firing of previously established place fields and rapidly induced new place field formation to produce feature selectivity in CA1 that is a function of both entorhinal cortex and CA3 input. Such selectivity could allow mixed network level representations that support context-dependent spatial maps.

Temporal synchrony and gamma-to-theta power conversion in the dendrites of CA1 pyramidal neurons.

Timing is a crucial aspect of synaptic integration. For pyramidal neurons that integrate thousands of synaptic inputs spread across hundreds of microns, it is thus a challenge to maintain the timing of incoming inputs at the axo-somatic integration site. Here we show that pyramidal neurons in the rodent hippocampus use a gradient of inductance in the form of hyperpolarization-activated cation-nonselective (HCN) channels as an active mechanism to counteract location-dependent temporal differences of dendritic inputs at the soma. Using simultaneous multi-site whole-cell recordings complemented by computational modeling, we find that this intrinsic biophysical mechanism produces temporal synchrony of rhythmic inputs in the theta and gamma frequency ranges across wide regions of the dendritic tree. While gamma and theta oscillations are known to synchronize activity across space in neuronal networks, our results identify a new mechanism by which this synchrony extends to activity within single pyramidal neurons with complex dendritic arbors.

Deletion of the hyperpolarization-activated cyclic nucleotide-gated channel auxiliary subunit TRIP8b impairs hippocampal Ih localization and function and promotes antidepressant behavior in mice.

Output properties of neurons are greatly shaped by voltage-gated ion channels, whose biophysical properties and localization within axodendritic compartments serve to significantly transform the original input. The hyperpolarization-activated current, I(h), is mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and plays a fundamental role in influencing neuronal excitability by regulating both membrane potential and input resistance. In neurons such as cortical and hippocampal pyramidal neurons, the subcellular localization of HCN channels plays a critical functional role, yet mechanisms controlling HCN channel trafficking are not fully understood. Because ion channel function and localization are often influenced by interacting proteins, we generated a knock-out mouse lacking the HCN channel auxiliary subunit, tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b). Eliminating expression of TRIP8b dramatically reduced I(h) expression in hippocampal pyramidal neurons. Loss of I(h)-dependent membrane voltage properties was attributable to reduction of HCN channels on the neuronal surface, and there was a striking disruption of the normal expression pattern of HCN channels in pyramidal neuron dendrites. In heterologous cells and neurons, absence of TRIP8b increased HCN subunit targeting to and degradation by lysosomes. Mice lacking TRIP8b demonstrated motor learning deficits and enhanced resistance to multiple tasks of behavioral despair with high predictive validity for antidepressant efficacy. We observed similar resistance to behavioral despair in distinct mutant mice lacking HCN1 or HCN2. These data demonstrate that interaction with the auxiliary subunit TRIP8b is a major mechanism underlying proper expression of HCN channels and I(h) in vivo, and suggest that targeting I(h) may provide a novel approach to treatment of depression.

Reversible Parkinsonism and T1W pallidal hyperintensities in acute liver failure.

We report on a young woman who survived acute liver failure (ALF) without liver transplant. During the ALF, she developed a disabling, levodopa-unresponsive, symmetrical Parkinsonism. This was characterized by severe bradykinesia, mild rigidity, mutism, and prominent gait impairment. Magnetic resonance imaging (MRI) showed bilateral T1W pallidal hyperintensities. Parkinsonism and MRI changes remitted in parallel with normalization of hepatic function. We implicate excessive pallidal manganese deposition secondary to ALF in the pathogenesis of this neuroradiological syndrome. Though hitherto unreported, we propose that Parkinsonism with T1W pallidal hyperintensities may not be uncommon in ALF.

Arrays of lipid bilayers and liposomes on patterned polyelectrolyte templates.

This paper presents novel methods to produce arrays of lipid bilayers and liposomes on patterned polyelectrolyte multilayers. We created the arrays by exposing patterns of poly(dimethyldiallylammonium chloride) (PDAC), polyethylene glycol (m-dPEG) acid, and poly(allylamine hydrochloride) (PAH) on polyelectrolyte multilayers (PEMs) to liposomes of various compositions. The resulting interfaces were characterized by total internal reflection fluorescence microscopy (TIRFM), fluorescence recovery after pattern photobleaching (FRAPP), quartz crystal microbalance (QCM), and fluorescence microscopy. Liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphate (monosodium salt) (DOPA) were found to preferentially adsorb on PDAC and PAH surfaces. On the other hand, liposome adsorption on sulfonated poly(styrene) (SPS) surfaces was minimal, due to electrostatic repulsion between the negatively charged liposomes and the SPS-coated surface. Surfaces coated with m-dPEG acid were also found to resist liposome adsorption. We exploited these results to create arrays of lipid bilayers by exposing PDAC, PAH and m-dPEG patterned substrates to DOPA/DOPC vesicles of various compositions. The patterned substrates were created by stamping PDAC (or PAH) on SPS-topped multilayers, and m-dPEG acid on PDAC-topped multilayers, respectively. This technique can be used to produce functional biomimetic interfaces for potential applications in biosensors and biocatalysis, for creating arrays that could be used for high-throughput screening of compounds that interact with cell membranes, and for probing, and possibly controlling, interactions between living cells and synthetic membranes.