Cell-to-cell communication is essential for the organization, coordination, and development of cellular networks and multi-cellular systems. Intercellular communication is mediated by soluble factors (including growth factors, neurotransmitters, and cytokines/chemokines), gap junctions, exosomes and recently described tunneling nanotubes (TNTs). It is unknown whether a combination of these communication mechanisms such as TNTs and gap junctions may be important, but further research is required. TNTs are long cytoplasmic bridges that enable long-range, directed communication between connected cells. The proposed functions of TNTs are diverse and not well understood but have been shown to include the cell-to-cell transfer of vesicles, organelles, electrical stimuli and small molecules. However, the exact role of TNTs and gap junctions for intercellular communication and their impact on disease is still uncertain and thus, the subject of much debate. The combined data from numerous laboratories indicate that some TNT mediate a long-range gap junctional communication to coordinate metabolism and signaling, in relation to infectious, genetic, metabolic, cancer, and age-related diseases. This review aims to describe the current knowledge, challenges and future perspectives to characterize and explore this new intercellular communication system and to design TNT-based therapeutic strategies.

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Tunneling Nanotubes and Gap Junctions-Their Role in Long-Range Intercellular Communication during Development, Health, and Disease Conditions.

Polyimides (PIs) represent a benchmark for high-performance polymers on the basis of a remarkable collection of valuable traits and accessible production pathways and therefore have incited serious attention from the ever-demanding medical field. Their characteristics make them suitable for service in hostile environments and purification or sterilization by robust methods, as requested by most biomedical applications. Even if PIs are generally regarded as “biocompatible”, proper analysis and understanding of their biocompatibility and safe use in biological systems deeply needed. This mini-review is designed to encompass some of the most robust available research on the biocompatibility of various commercial or noncommercial PIs and to comprehend their potential in the biomedical area. Therefore, it considers (i) the newest concepts in the field, (ii) the chemical, (iii) physical, or (iv) manufacturing elements of PIs that could affect the subsequent biocompatibility, and, last but not least, (v) in vitro and in vivo biocompatibility assessment and (vi) reachable clinical trials involving defined polyimide structures. The main conclusion is that various PIs have the capacity to accommodate in vivo conditions in which they are able to function for a long time and can be judiciously certified as biocompatible.

https://www.mdpi.com/1996-1944/12/19/3166/pdf

Biocompatibility of Polyimides: A Mini-Review

We demonstrate a novel approach to femtosecond microfabrication of transparent dielectrics, which employs nondiffracting Bessel beams instead of the conventionally used Gaussian beams. The main advantage of Bessel beams is the possibility of recording linear photomodified tracks, extending along the lines of nondiffractive beam propagation without sample translation, as would be required for Gaussian beams. Recording of patterns with an aspect ratio of up to 102–103 in vitreous silica using amplified femtosecond Ti:saphire laser pulses is demonstrated.

Application of Bessel Beams for Microfabrication of Dielectrics by Femtosecond Laser : Instrumentation, Measurement, and Fabrication Technology

Diffraction is a phenomenon related to the wave nature of light and arises when a propagating wave comes across an obstacle. Consequently, the wave can be transformed in amplitude or phase and diffraction occurs. Those parts of the wavefront avoiding an obstacle form a diffraction pattern after interfering with each other. In this review paper, we have discussed the topic of non-diffractive beams, explicitly Bessel beams. Such beams provide some resistance to diffraction and hence are hypothetically a phenomenal alternate to Gaussian beams in several circumstances. Several outstanding applications are coined to Bessel beams and have been employed in commercial applications. We have discussed several hot applications based on these magnificent beams such as optical trapping, material processing, free-space long-distance self-healing beams, optical coherence tomography, superresolution, sharp focusing, polarization transformation, increased depth of focus, birefringence detection based on astigmatic transformed BB and encryption in optical communication. According to our knowledge, each topic presented in this review is justifiably explained.

Bessel Beam: Significance and Applications-A Progressive Review.

Intercellular communication is essential for the development and maintenance of multicellular organisms. Tunneling nanotubes (TNTs) are a recently recognized means of long and short distance communication between a wide variety of cell types. TNTs are transient filamentous membrane protrusions that connect cytoplasm of neighboring or distant cells. Cytoskeleton fiber-mediated transport of various cargoes occurs through these tubules. These cargoes range from small ions to whole organelles. TNTs have been shown to contribute not only to embryonic development and maintenance of homeostasis, but also to the spread of infectious particles and resistance to therapies. These functions in the development and progression of cancer and infectious disease have sparked increasing scrutiny of TNTs, as their contribution to disease progression lends them a promising therapeutic target. Herein, we summarize the current knowledge of TNT structure and formation as well as the role of TNTs in pathology, focusing on viral, prion, and malignant disease. We then discuss the therapeutic possibilities of TNTs in light of their varied functions. Despite recent progress in the growing field of TNT research, more studies are needed to precisely understand the role of TNTs in pathological conditions and to develop novel therapeutic strategies.

Cell communication by tunneling nanotubes: Implications in disease and therapeutic applications.

Bessel beams are perfect candidates for laser microprocessing of transparent materials due to generation of high aspect ratio micro voids [1], and ability to control micro crack formation enables to efficiently cut them [2, 3]. The crack propagation direction is controlled by inducing asymmetry to beam profile [3], and allows ultra-fast glass cutting over non-straight lines. The laser-matter interaction of various nondiffracting beams is heavily investigated and their utilisation for laser microprocessing is soon to be expected. Vector beams that are more exotic than scalar counterparts and can have additional beneficial properties for micro-manufacturing of materials. For instance, vector Bessel beam has a doughnut shaped intensity profile with complex spatial distribution of polarisation and can be de-composed to two transverse polarisation intensity components [4].

Generation of Vector Bessel Beams and their Application for Laser Microprocessing of Transparent Materials

Geometrical phase (also known as Pancharatnam-Berry phase [1,2].) elements and their applications are booming nowadays: from devices like high NA metalenses to special optics like s-waveplates [3], from wavelengths in the ultraviolet to the THz diapason. The reason behind such flexibility is due to variety of different production approaches — lithography based, sculptured coatings etc. and due to the varying orientation and individual properties of sub-elements of the GPE. Such elements can act as both scalar and vectorial diffractive optical elements (or as shapers of the spatial spectra of the input beam), but usually their vectorial properties are largely ignored due to the complexity of mastering phases and amplitudes of both transverse components.

Femtosecond Laser Microfabrication of Pancharatnam-Berry Phase Elements for the Formation of Optical Needles in Transparent Materials

Zeroth order Bessel beams are widely used in laser micromachining of transparent materials. The small diameter of central core and elongated focus enables to generate high aspect ratio voids. The simplest way to generate this beam is to induce a conical shape phase with an axicon. However, the quality of the axicon tip is very crucial to generate smooth Bessel beams since it is known that a blunt axicon tip induces large intensity modulation in propagation direction. Alternative Bessel beam generation method is to use a Diffractive Optical Elements (DOEs) that do not suffer from previously mentioned problem. In this work we demonstrate generation of a zeroth order Bessel beam with Geometric Phase Optical Elements (GPOEs) (manufactured by Workshop of Photonics) acting as a diffractive beam shaping element. Having absolute control of induced beam phase, we have modified mask phase so that half of it had additional phase shift or spatial transposition resulting in creation of fanciful induced beam phase patterns. With the use of laser beam propagation numerical modeling we show that these new phase masks can create various beam transverse intensity patterns such as asymmetrical central core, generation of multiple peaks or even large rings that are highly demanded for various laser micromachining applications. We have chosen couple of most perspective beam shapes and manufactured GPOEs to generate them. The experimentally generated beams were compared to numerical simulations. As the GPOEs are able to work with high power pulses we have also investigated induced transparent material modifications.

Generation of Bessel type beams via phase shifted axicons encoded in geometrical phase elements

During the last decade the zeroth order Bessel-Gauss laser beam has found many uses in the transparent material processing. The high aspect ratio channels can be created that slice through various thin transparent materials and increase the efficiency of cutting. However, the generation of high-quality Bessel-Gauss beam remains a challenge due to imperfection of glass axicon manufacturing, i.e. rounded tip, not smooth surface etc. These imperfections generate intensity modulation along propagation axis or even modify transversal central core intensity distribution, that results in worsening of micro-machining quality. The diffractive optical element (DOE) is a great alternative that do not suffer from previously mentioned problems. In this study we show the possibility of generating high quality Bessel-type beams with geometric phase optical elements (GPOEs) (manufactured by Workshop of Photonics). These elements act as precise flat DOEs that have very high diffraction efficiency (>90%), high optical damage threshold and can be freely customized for specific needs. Therefore, with the use of high-power laser they can be applied to process transparent materials. In this work, controllable phase shifts are implemented in axicon phase masks to create unique and fanciful Bessel-type beams as well as asymmetric core beams for thin glass modification/cutting application. Using numerical simulations and experimental data we compare performance of GPOEs and demonstrate thin glass processing using powerful laser with reshaped intensity distribution by GPOE.

Thin glass processing using Bessel-type beams generated with spatially phase-shifted axicons

The invention relates to volume modification of transparent materials (5) by means of ultrashort laser pulses. A method of manufacturing of highly transparent spatially variant waveplates (5) includes focussing Gaussian laser beam (2) with pulse duration 500 fs to 2000 fs inside of material (5) transparent to laser wavelength building self-organizing structures of nanoplates (6). The workpiece (5) is moved in three coordinates relatively to beam focus along desired line. A combination of focus area, pulse repetition rate, energy and velocity of movement is selected to locate said structures inside of the workpiece (5) for acting as birefringent optical elements with specific retardance. Energy of pulses exceeds the threshold of building nanoplates (6) in part of the focal area limited by -crf2 and o/2 where β is standard deviation from maximum of Gaussian function. Energy of pulses creating nanoplates (6) is accumulated in said area from the sequence of 1000 to 2000 pulses in total not exceeding 0,2-0, 3 pj.

Orestas Ulčinas

Papers

Generation of Vector Bessel Beams and their Application for Laser Microprocessing of Transparent Materials

Femtosecond Laser Microfabrication of Pancharatnam-Berry Phase Elements for the Formation of Optical Needles in Transparent Materials

Generation of Bessel type beams via phase shifted axicons encoded in geometrical phase elements

Thin glass processing using Bessel-type beams generated with spatially phase-shifted axicons

Method of manufacturing of spatially modulated waveplates