The suprapatellar fat pad: A histotopographic comparative study.

The suprapatellar fat pad is an adipose tissue located in the anterior knee whose role in osteoarthritis is still debated. Considering that anatomy drives function, the aim of this histotopographic study was to investigate the specific morphological features of the suprapatellar fat pad versus the infrapatellar fat pad in the absence of osteoarthritis, for a broad comparative analysis. Suprapatellar fat pad and infrapatellar fat pad tissue samples (n = 10/group) underwent microscopical/immunohistochemical staining and transmission electron microscopy analysis; thus, tissue-specific characteristics (i.e., vessels and nerve endings presence, lobuli, adipocytes features, septa), including extracellular matrix proteins prevalence (collagens, elastic fibers), were focused. Multiphoton microscopy was also adopted to evaluate collagen fiber orientation within the samples by Fast Fourier Transform (coherency calculation). The absence of inflammation was confirmed, and comparable counted vessels and nerve endings were shown. Like the infrapatellar fat pad, the suprapatellar fat pad appeared as a white adipose tissue with lobuli and septa of comparable diameter and thickness, respectively. Tissue main characteristics were also proved by both semithin sections and transmission electron microscopy analysis. The suprapatellar fat pad adipocytes were roundish and with a smaller area, perimeter, and major axis than that of the infrapatellar fat pad. The collagen fibers surrounding them showed no significant difference in collagen type I and significantly higher values for collagen type III in the infrapatellar fat pad group. Regarding the septa, elastic fiber content was statistically comparable between the two groups, even though more represented by the suprapatellar fat pad. Total collagen was significantly higher in the infrapatellar fat pad and comparing collagen type I and type III they were similarly represented in the whole cohort despite collagen type I appearing to be higher in the infrapatellar fat pad than in the suprapatellar fat pad and vice versa for collagen type III. Second harmonic generation microscopy confirmed through coherency calculation an anisotropic distribution of septa collagen fibers. From a mechanical point of view, the different morphological characteristics determined a major stiffness for the infrapatellar fat pad with respect to the suprapatellar fat pad. This study provides, for the first time, a topographic description of the suprapatellar fat pad compared to the infrapatellar fat pad; differences between the two groups may be attributed to a different anatomical location within the knee; the results gathered here may be useful for a more complete interpretation of osteoarthritis disease, involving not only cartilage but the whole joint.

Strongly Interacting Photons in 2D Waveguide QED.

One-dimensional confinement in waveguide quantum electrodynamics (QED) plays a crucial role to enhance light-matter interactions and to induce a strong quantum nonlinear optical response. In two or higher-dimensional settings, this response is reduced since photons can be emitted within a larger phase space, opening the question whether strong photon-photon interaction can be still achieved. In this study, we positively answer this question for the case of a 2D square array of atoms coupled to the light confined into a two-dimensional waveguide. More specifically, we demonstrate the occurrence of long-lived two-photon repulsive and bound states with genuine 2D features. Furthermore, we observe signatures of these effects also in free-space atomic arrays in the form of weakly subradiant in-band scattering resonances. Our findings provide a paradigmatic signature of the presence of strong photon-photon interactions in 2D waveguide QED.

Silicon metaoptics for the compact generation of perfect vector beams in the telecom infrared.

Perfect vortices have attracted considerable attention as orbital angular momentum (OAM) beams with customizable ring-like intensity distribution. More recently, the non-separable combination of perfect vortices with opposite OAMs and spins, yielding so-called perfect vector beams, has further expanded their applications in the fields of optical manipulation and imaging, high-resolution lithography, and telecommunications. Exploiting the combined manipulation of dynamic and geometric phases using silicon anisotropic metaunits, here we present the design, fabrication, and characterization of novel, to the best of our knowledge, dielectric metaoptics for the compact generation of perfect vector beams in the telecom infrared using a single metasurface. These devices pave the way to integrated optical architectures with applications in information and communication technologies in both the classical and quantum regimes.

Covalently Grafted Peptides to Decellularized Pericardium: Modulation of Surface Density.

The covalent functionalization of synthetic peptides allows the modification of different biomaterials (metallic, polymeric, and ceramic), which are enriched with biologically active sequences to guide cell behavior. Recently, this strategy has also been applied to decellularized biological matrices. In this study, the covalent anchorage of a synthetic peptide (REDV) to a pericardial matrix decellularized via Schiff base is realized starting from concentrated peptide solutions (10-4 M and 10-3 M). The use of a labeled peptide demonstrated that as the concentration of the working solution increased, the surface density of the anchored peptide increased as well. These data are essential to pinpointing the concentration window in which the peptide promotes the desired cellular activity. The matrices were extensively characterized by Water Contact Angle (WCA) analysis, Differential Scanning Calorimetry (DSC) analysis, geometric feature evaluation, biomechanical tests, and preliminary in vitro bioassays.

Porcine Small Intestinal Submucosa (SIS) as a Suitable Scaffold for the Creation of a Tissue-Engineered Urinary Conduit: Decellularization, Biomechanical and Biocompatibility Characterization Using New Approaches.

Bladder cancer (BC) is among the most common malignancies in the world and a relevant cause of cancer mortality. BC is one of the most frequent causes for bladder removal through radical cystectomy, the gold-standard treatment for localized muscle-invasive and some cases of high-risk, non-muscle-invasive bladder cancer. In order to restore urinary functionality, an autologous intestinal segment has to be used to create a urinary diversion. However, several complications are associated with bowel-tract removal, affecting patients' quality of life. The present study project aims to develop a bio-engineered material to simplify this surgical procedure, avoiding related surgical complications and improving patients' quality of life. The main novelty of such a therapeutic approach is the decellularization of a porcine small intestinal submucosa (SIS) conduit to replace the autologous intestinal segment currently used as urinary diversion after radical cystectomy, while avoiding an immune rejection. Here, we performed a preliminary evaluation of this acellular product by developing a novel decellularization process based on an environmentally friendly, mild detergent, i.e., Tergitol, to replace the recently declared toxic Triton X-100. Treatment efficacy was evaluated through histology, DNA, hydroxyproline and elastin quantification, mechanical and insufflation tests, two-photon microscopy, FTIR analysis, and cytocompatibility tests. The optimized decellularization protocol is effective in removing cells, including DNA content, from the porcine SIS, while preserving the integrity of the extracellular matrix despite an increase in stiffness. An effective sterilization protocol was found, and cytocompatibility of treated SIS was demonstrated from day 1 to day 7, during which human fibroblasts were able to increase in number and strongly organize along tissue fibres. Taken together, this in vitro study suggests that SIS is a suitable candidate for use in urinary diversions in place of autologous intestinal segments, considering the optimal results of decellularization and cell proliferation. Further efforts should be undertaken in order to improve SIS conduit patency and impermeability to realize a future viable substitute.

Multipole-phase division multiplexing.

The control of structured waves has recently opened innovative scenarios in the perspective of radiation propagation, advanced imaging, and light-matter interaction. In information and communication technology, the spatial degrees of freedom offer a wider state space to carry many channels on the same frequency or increase the dimensionality of quantum protocols. However, spatial decomposition is much more arduous than polarization or frequency multiplexing, and very few practical examples exist. Among all, beams carrying orbital angular momentum gained a preeminent role, igniting a variety of methods and techniques to generate, tailor, and measure that property. In a more general insight into structured-phase beams, we introduce here a new family of wave fields having a multipole phase. These beams are devoid of phase singularities and described by two continuous spatial parameters which can be controlled in a practical and compact way via conformal optics. The outlined framework encompasses multiplexing, propagation, and demultiplexing as a whole for the first time, describing the evolution and transformation of wave fields in terms of conformal mappings. With its potentialities, versatility, and ease of implementation, this new paradigm introduces a novel playground for space division multiplexing, suggesting unconventional solutions for light processing and free-space communications.

Label-Free Multiphoton Microscopy: Much More Than Fancy Images.

Multiphoton microscopy has recently passed the milestone of its first 30 years of activity in biomedical research. The growing interest around this approach has led to a variety of applications from basic research to clinical practice. Moreover, this technique offers the advantage of label-free multiphoton imaging to analyze samples without staining processes and the need for a dedicated system. Here, we review the state of the art of label-free techniques; then, we focus on two-photon autofluorescence as well as second and third harmonic generation, describing physical and technical characteristics. We summarize some successful applications to a plethora of biomedical research fields and samples, underlying the versatility of this technique. A paragraph is dedicated to an overview of sample preparation, which is a crucial step in every microscopy experiment. Afterwards, we provide a detailed review analysis of the main quantitative methods to extract important information and parameters from acquired images using second harmonic generation. Lastly, we discuss advantages, limitations, and future perspectives in label-free multiphoton microscopy.

Design of continuously variant metasurfaces for conformal transformation optics.

Metasurfaces optics and structured light represent two emerging paradigms which are revolutionizing optics in a wide range of fields, from imaging to telecommunications, both in the classical and single-photon regimes. In this work, we present and describe a method for the design of high-resolution geometric-phase metasurfaces in the form of continuously variant sub-wavelength gratings, and we demonstrate how this technique is suitable for harmonic phase masks implementing conformal optical transformations. In this framework, we revisit the metasurface design of blazed gratings and spiral phase plates, the so-called q-plates, and we extend the method to the metasurface implementation of two conformal mappings, the log-pol and the circular-sector transformation, which have been exploited successfully to perform the generation, sorting and manipulation of structured light beams carrying orbital angular momentum.

Grating-Coupled Surface Plasmon Resonance (GC-SPR) Optimization for Phase-Interrogation Biosensing in a Microfluidic Chamber.

Surface Plasmon Resonance (SPR)-based sensors have the advantage of being label-free, enzyme-free and real-time. However, their spreading in multidisciplinary research is still mostly limited to prism-coupled devices. Plasmonic gratings, combined with a simple and cost-effective instrumentation, have been poorly developed compared to prism-coupled system mainly due to their lower sensitivity. Here we describe the optimization and signal enhancement of a sensing platform based on phase-interrogation method, which entails the exploitation of a nanostructured sensor. This technique is particularly suitable for integration of the plasmonic sensor in a lab-on-a-chip platform and can be used in a microfluidic chamber to ease the sensing procedures and limit the injected volume. The careful optimization of most suitable experimental parameters by numerical simulations leads to a 30⁻50% enhancement of SPR response, opening new possibilities for applications in the biomedical research field while maintaining the ease and versatility of the configuration.

Test of mode-division multiplexing and demultiplexing in free-space with diffractive transformation optics.

In recent years, mode-division multiplexing (MDM) has been proposed as a promising solution in order to increase the information capacity of optical networks both in free-space and in optical fiber transmission. Here we present the design, fabrication and test of diffractive optical elements for mode-division multiplexing based on optical transformations in the visible range. Diffractive optics have been fabricated by means of 3D high-resolution electron beam lithography on polymethylmethacrylate resist layer spun over a glass substrate. The same optical sequence was exploited both for input-mode multiplexing and for output-mode sorting after free-space propagation. Their high miniaturization level and efficiency make these optical devices ideal for integration into next-generation platforms for mode-division (de)multiplexing in telecom applications.

Compact sorting of optical vortices by means of diffractive transformation optics.

The orbital angular momentum (OAM) of light has recently attracted a growing interest as a new degree of freedom in order to increase the information capacity of today's optical networks, both for free-space and optical fiber transmission. Here we present our work of design, fabrication, and optical characterization of diffractive optical elements for compact OAM mode division demultiplexing based on optical transformations. Samples have been fabricated with 3D high-resolution electron beam lithography on a polymethylmethacrylate resist layer spun over a glass substrate. Their high compactness and efficiency make these optical devices promising for integration into next-generation platforms for OAM modes processing in telecom applications.

Label-free efficient and accurate detection of cystic fibrosis causing mutations using an azimuthally rotated GC-SPR platform.

Plasmonic nanosensors are candidates for the development of new sensors with low detection limits, high sensitivity, and specificity for target detection: these characteristics are of critical importance in the screening of mutations responsible for inherited diseases. In this work, we focused our study on the detection of some of the most frequent mutations responsible for cystic fibrosis (CF) among the Italian population. For the detection of the CF mutations we adopted a recently developed and highly sensitive Grating Coupled-Surface Plasmon Resonance (GC-SPR) enhanced spectroscopy method for label-free molecular identification exploiting a conical illumination configuration. Gold sinusoidal gratings functionalized with heterobifunctional PEG were used as sensing surfaces, and the specific biodetection was achieved through the coupling with DNA hairpin probes designed for single nucleotide discrimination. Such substrates were used to test unlabeled PCR amplified homozygous wild type (wt) and heterozygous samples, deriving from clinical samples, for the screened mutations. Hybridization conditions were optimized to obtain the maximum discrimination ratio (DR) between the homozygous wild type and the heterozygous samples. SPR signals obtained from hybridizing wild type and heterozygous samples show DRs able to identify univocally the correct genotypes, as confirmed by fluorescence microarray experiments run in parallel. Furthermore, SPR genotyping was not impaired in samples containing unrelated DNA, allowing the platform to be used for the concomitant discrimination of several alleles also scalable for a high throughput screening setting.

Sub-wavelength confinement of the orbital angular momentum of light probed by plasmonic nanorods resonances.

We discuss how the topological charge of an OAM-carrying plasmon (Plasmonic Vortex) can be probed by monitoring the near-field response of plasmonic nanostructures suitably arranged inside a Plasmonic Vortex Lens. The turning "on" or "off" of four gold nanorods, detected by a Scanning Near field Optical Microscope (SNOM), acts as a fingerprint of the OAM state of the PV at the nanoscale. Different configurations are studied numerically, the integrated structure is fabricated and near field characterization is performed for a particularly meaningful case.

Resonance properties of thick plasmonic split ring resonators for sensing applications.

We investigate in detail the optical response of dense split ring resonator (SRR) arrays as a function of their thickness, for normally impinging light in the VIS-NIR spectral range. We find that, for sufficiently tall SRRs, several vertical Fabry-Perot resonances can be excited, which may interact with the well-known horizontal SRR resonant paths. Furthermore, we analyze the possibility to exploit these nanostructures to detect bio-chemical quantities. In particular, we find that the coexistence of vertical and horizontal resonances yields an increased sensitivity. Well ordered, large arrays of thick SRRs are obtained by exploiting a fabrication process based on X-Ray Lithography. A very good agreement is found between numerical and measured transmittances. A preliminary detection test evidences the potential of this geometry as a sensing platform.

Bilayer holey plasmonic vortex lenses for the far field transmission of pure orbital angular momentum light states.

We report the design of a holey plasmonic vortex lens (PVL) structure able to couple circularly polarized impinging light to a plasmonic vortex in the form of the fundamental TM mode of a metal-insulator-metal plasmonic waveguide. The field transmitted through the hole milled at the center of the second metal layer of the structure is characterized by a well-defined spiral harmonic, entirely determined by the spin of impinging light and by the chirality of the PVL structure. Scattering finite elements simulations are presented for single layer standard PVLs and for bilayer ones, comparing the spiral spectra of the transmitted field and the efficiencies of the architectures.

Hybrid Materials for Vascular Applications: A Preliminary In Vitro Assessment.

The production of biomedical devices able to appropriately interact with the biological environment is still a great challenge. Synthetic materials are often employed, but they fail to replicate the biological and functional properties of native tissues, leading to a variety of adverse effects. Several commercial products are based on chemically treated xenogeneic tissues: their principal drawback is due to weak mechanical stability and low durability. Recently, decellularization has been proposed to bypass the drawbacks of both synthetic and biological materials. Acellular materials can integrate with host tissues avoiding/mitigating any foreign body response, but they often lack sufficient patency and impermeability. The present paper investigates an innovative approach to the realization of hybrid materials that combine decellularized bovine pericardium with polycarbonate urethanes. These hybrid materials benefit from the superior biocompatibility of the biological tissue and the mechanical properties of the synthetic polymers. They were assessed from physicochemical, structural, mechanical, and biological points of view; their ability to promote cell growth was also investigated. The decellularized pericardium and the polymer appeared to well adhere to each other, and the two sides were distinguishable. The maximum elongation of hybrid materials was mainly affected by the pericardium, which allows for lower elongation than the polymer; this latter, in turn, influenced the maximum strength achieved. The results confirmed the promising features of hybrid materials for the production of vascular grafts able to be repopulated by circulating cells, thus, improving blood compatibility.

Dual-functional metalenses for the polarization-controlled generation of focalized vector beams in the telecom infrared.

The availability of static tiny optical devices is mandatory to reduce the complexity of optical paths that typically use dynamic optical components and/or many standard elements for the generation of complex states of light, leading to unprecedented levels of miniaturization and compactness of optical systems. In particular, the design of flat and integrated optical elements capable of multiple vector beams generation with high resolution in the visible and infrared range is very attractive in many fields, from life science to information and communication technology. In this regard, we propose dual-functional transmission dielectric metalenses that act simultaneously on the dynamic and geometric phases in order to manipulate independently right-handed and left-handed circularly polarized states of light and generate focused vector beams in a compact and versatile way. In the specific, starting from the mathematical fundamentals for the compact generation of vector beams using dual-functional optical elements, we provide the numerical algorithms for the computation of metaoptics and apply those techniques to the design and fabrication of silicon metalenses which are able to generate and focus different vector beams in the telecom infrared, depending on the linear polarization state in input. This approach provides new integrated optics for applications in the fields of high-resolution microscopy, optical manipulation, and optical communications, both in the classical and single-photon regimes.

Tergitol Based Decellularization Protocol Improves the Prerequisites for Pulmonary Xenografts: Characterization and Biocompatibility Assessment.

Right ventricle outflow tract obstruction (RVOTO) is a congenital pathological condition that contributes to about 15% of congenital heart diseases. In most cases, the replacement of the right ventricle outflow in pediatric age requires subsequent pulmonary valve replacement in adulthood. The aim of this study was to investigate the extracellular matrix scaffold obtained by decellularization of the porcine pulmonary valve using a new detergent (Tergitol) instead of Triton X-100. The decellularized scaffold was evaluated for the integrity of its extracellular matrix (ECM) structure by testing for its biochemical and mechanical properties, and the cytotoxicity/cytocompatibility of decellularized tissue was assessed using bone marrow-derived mesenchymal stem cells. We concluded that Tergitol could remove the nuclear material efficiently while preserving the structural proteins of the matrix, but without an efficient removal of the alpha-gal antigenic epitope. Therefore, Tergitol can be used as an alternative detergent to replace the Triton X-100.

Preliminary In Vitro Assessment of Decellularized Porcine Descending Aorta for Clinical Purposes.

Conduit substitutes are increasingly in demand for cardiovascular and urological applications. In cases of bladder cancer, radical cystectomy is the preferred technique: after removing the bladder, a urinary diversion has to be created using autologous bowel, but several complications are associated with intestinal resection. Thus, alternative urinary substitutes are required to avoid autologous intestinal use, preventing complications and facilitating surgical procedures. In the present paper, we are proposing the exploitation of the decellularized porcine descending aorta as a novel and original conduit substitute. After being decellularized with the use of two alternative detergents (Tergitol and Ecosurf) and sterilized, the porcine descending aorta has been investigated to assess its permeability to detergents through methylene blue dye penetration analysis and to study its composition and structure by means of histomorphometric analyses, including DNA quantification, histology, two-photon microscopy, and hydroxyproline quantification. Biomechanical tests and cytocompatibility assays with human mesenchymal stem cells have been also performed. The results obtained demonstrated that the decellularized porcine descending aorta preserves its major features to be further evaluated as a candidate material for urological applications, even though further studies have to be carried out to demonstrate its suitability for the specific application, by performing in vivo tests in the animal model.

Development and In Vitro/In Vivo Comparative Characterization of Cryopreserved and Decellularized Tracheal Grafts.

Tracheal reconstruction represents a challenge when primary anastomosis is not feasible. Within this scenario, the study aim was to develop a new pig-derived decellularized trachea (DecellT) to be compared with the cryopreserved counterpart (CryoT) for a close predictive analysis. Tracheal segments underwent decellularization by a physical + enzymatic + chemical method (12 cycles); in parallel, cryopreserved samples were also prepared. Once decellularized (histology/DNA quantification), the two groups were characterized for Alpha-Gal epitopes/structural proteins (immunohistochemistry/histology/biochemical assays/second harmonic generation microscopy)/ultrastructure (Scanning Electron Microscopy (SEM))/mechanical behaviour. Cytotoxicity absence was assessed in vitro (extract-test assay/direct seeding, HM1SV40 cell line) while biocompatibility was verified in BALB/c mice, followed by histological/immunohistochemical analyses and SEM (14 days). Decellularization effectively removed Alpha-Gal epitopes; cartilage histoarchitecture was retained in both groups, showing chondrocytes only in the CryoT. Cryopreservation maintained few respiratory epithelium sparse cilia, not detectable in DecellT. Focusing on ECM, preserved structural/ultrastructural organization and collagen content were observed in the cartilage of both; conversely, the GAGs were significantly reduced in DecellT, as confirmed by mechanical study results. No cytotoxicity was highlighted by CryoT/DecellT in vitro, as they were also corroborated by a biocompatibility assay. Despite some limitations (cells presence/GAGs reduction), CryoT/DecellT are both appealing options, which warrant further investigation in comparative in vivo studies.