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Samples containing small cellular particles (SCPs) isolated from blood plasma (BP), washed erythrocytes (BE), spruce needle homogenate (S), suspension of flagellae of microalgae Tetraselmis chuii (T), conditioned culture media of microalgae Phaeodactylum tricornutum (P) and liposomes (L) were assessed by interferometric light microscopy (ILM) (Boccara et al., 2016) for their number density and hydrodynamic radius (Rh) by using equipment Videodrop (Myriade, Paris, France). Each particle that was included in the analysis was tracked by recording a video and processed individually by using the associated software QVIR 2.6.0 (Myriade, Paris, France). Sample legend and preparation: B1/IS Washed erythrocytes. Blood was centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia) to sediment the erythrocytes. The supernatant from above including the buffy coat was removed. Erythrocytes were resuspended into PBS, mixed by turning the epruvette upside-down and centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia). The supernatant was removed and replaced by PBS. Erythrocytes were resuspended in PBS, mixed by turning the epruvette upside-down and centrifuged for 30 minutes at 500g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia). B2/IS Isolate from plasma. To obtain plasma, blood was centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia) to sediment the erythrocytes. Plasma above the buffy coat was collected into a 4 mL sterilized plastic tube and mixed by turning the tube upside down several times. Plasma was aliquoted into 250 \(\mu \)L samples in Eppendorf tubes and centrifuged at 17,570g and room temperature for 10 minutes in the Centric 200R centrifuge with Lilliput rotor (Domel, Železniki, Slovenia). In each aliquot, upper 200 \(\mu \)L of supernatant was replaced by PBS, resuspended and centrifuged again at 17,570 g and room temperature for 10 minutes in the Centric 200R centrifuge with Lilliput rotor (Domel, Železniki, Slovenia). 200 \(\mu \)L of supernatant was removed and the pellet was suspended in 80 \(\mu \)L of PBS. B3/SN Supernatant from plasma. To obtain plasma, blood was centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia) to sediment the erythrocytes. 250 \(\mu \)L of supernatant from above the buffy coat was collected into Eppendorf tube and centrifuged at 17,570g and room temperature for 10 minutes in the Centric 200R centrifuge with Lilliput rotor (Domel, Železniki, Slovenia). Upper 200 \(\mu \)L of supernatant was collected to form B3/SN sample. B4/SN Supernatant from centrifugation of PBS suspension of plasma EPs. Blood was centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia) to sediment the erythrocytes. 250 \(\mu \)L of supernatant from above the buffy coat was collected into Eppendorf tube and centrifuged at 17,570g and room temperature for 10 minutes in the Centric 200R centrifuge with Lilliput rotor (Domel, Železniki, Slovenia). Upper 200 \(\mu \)L of supernatant was replaced by PBS, resuspended and centrifuged again at 17,570 g and room temperature for 10 minutes in the Centric 200R centrifuge with Lilliput rotor (Domel, Železniki, Slovenia). Upper 200 \(\mu \)L of supernatant was collected to form B4/SN sample. B5/IS, B8/IS Isolates from suspension of aged washed erythrocytes. Blood was centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia) to sediment the erythrocytes. The supernatant from above the buffy coat was removed. The erythrocytes were resuspended into PBS by turning the epruvette upside-down and centrifuged for 10 min at 300 g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia). The supernatant was removed and replaced by PBS. Erythrocytes were resuspended in PBS, mixed by turning the epruvette upside-down and centrifuged for 30 minutes at 500g and 18 °C (centrifuge Centric 400/R, Domel, Slovenia). Supernatant was removed, replaced by fresh PBS and mixed by turning the epruvette upside-down. The washed erythrocytes in buffer were stored at 4 °C. On day 6 after blood collection, the erythrocyte suspension was homogenized by gently inverting the tube 5–10 times. Samples were then subjected to sequential centrifugation of supernatants for 10 min at 500 g, 2000 g, and 4000 g, all at 4 °C in the centrifuge Centric 400/R (Domel, Slovenia). After the last step, the supernatant was subjected to centrifugation at 50,000 g, and 4 °C for 70 min, in an ultracentrifuge Beckman L8–70M with rotor SW55Ti (Thermo Fisher Scientific, USA). The pelleted vesicles were resupended in 5 mL of PBS–citrate and centrifuged at 50,000 g and at 4 °C for 70 min. Pellet was resuspended in 1 mL PBS–citrate to obtain the isolate which was stored at 4 °C until analysed. S1/IS, S6/IS, S9/IS, S11/IS, S12/IS, S13/IS Isolates from spruce needle homogenate. Branches of spruce were cut from the Picea abies tree and used immediately. Branches were immersed into 1.5 L of water at 30 oC with 10 mL of sodium hypochlorite (NaClO, 0.1 %) for 1 hour. The branches were rinsed with water. The needles were cut off from the branches. 50.0 g of wet needles were immersed in 300 mL of ultraclean water and stirred for 1 minute in KOIOS 850W Smoothie Bullet Blender (KOIOS, Neweg, USA). The homogenate was filtered through 0.5 mm nylon net cloth to remove larger particles. EPs were isolated by differential ultracentrifugation. The cells were removed by low-speed centrifugation (300 g, 10 min, 4°C, centrifuge Centric 260R with rotor RA 6/50 (Domel, Slovenia)), using 50 mL conical centrifuge tubes (ref. S.078.02.008.050, Isolab Laborgeräte GmbH, Germany); and 2000 g, 10 min, 4°C (Centric 400R centrifuge with rotor RS4/100 (Domel, Slovenia)), using 15 mL conical centrifuge tubes (ref. S.078.02.001.050, Isolab Laborgeräte GmbH, Germany). Each step was repeated twice. Then, the cell-depleted medium was centrifuged twice at 10 000 g and 4°C for 30 min (Beckman L8-70M ultracentrifuge, rotor SW55Ti (Beckman Coulter, USA)), using thin-wall polypropylene centrifuge tubes (ref. 326819, Beckman Coulter, USA) to remove larger cell debris. Finally, EPs were pelleted by ultracentrifugation at 118 000 g and 4°C, for 70 min in the same type of ultracentrifuge and ultracentrifuge tubes. The pellet was resuspended in 50 µL of ultraclean water. T1/IS Isolate from suspension of flagellae of Tetraselmis chuii microalgae. Culture of Tetraselmis chuii CCAP 66/21b from the Culture Collection of Algae and Protozoa (CCAP) of SAMS (Oban, Scotland) were grown in artificial seawater (Reef Crystals, Aquarium Systems, France). 22 g of salt was dissolved in one litre of distilled water, sterile filtered (0.2-micron cellulose filters, ref. 11107-47-CAN, Sartorius Stedim Biotech GmbH, Germany), autoclaved, and supplemented with Guillard’s (F/2) Marine Water Enrichment Solution (ref. G0154, Sigma Aldrich, USA)18. Cultures were grown in a respirometer (Echo, Slovenia) in 0.5-L borosilicate bottles, at 20 °C and 20 % illumination with a 14-hour light / 10-hour dark cycle, with aeration of 0.2 L/min. Microalgae were harvested when a stable logarithmic growth phase was reached (about one months after inoculation). Flagella were removed from cells by a pH shock: in 10 mL of cell culture, 10 µL of HCl (1 M) was added and distributed over the sample by rapid stirring. Removal of the flagella was confirmed under inverted light microscope (Eclipse TE2000-S, Nikon, Tokio, Japan). Then, 10 µL of NaOH (1 M) was added to the culture to re-establish the initial pH in the culture. EPs were isolated from a 10 mL sample by differential ultracentrifugation, The cells were removed by low-speed centrifugation (300 g, 10 min, 4°C, centrifuge Centric 260R with rotor RA 6/50 (Domel, Slovenia)), using 50 mL conical centrifuge tubes (ref. S.078.02.008.050, Isolab Laborgeräte GmbH, Germany); and 2000 g, 10 min, 4°C (Centric 400R centrifuge with rotor RS4/100 (Domel, Slovenia)), using 15 mL conical centrifuge tubes (ref. S.078.02.001.050, Isolab Laborgeräte GmbH, Germany). Each step was repeated twice. Then, the cell-depleted medium was centrifuged twice at 10 000 g and 4°C for 30 min (Beckman L8-70M ultracentrifuge, rotor SW55Ti (Beckman Coulter, USA)), using thin-wall polypropylene centrifuge tubes (ref. 326819, Beckman Coulter, USA) to remove larger cell debris. Finally, EPs were pelleted by ultracentrifugation at 118 000 g and 4°C, for 70 min in the same type of ultracentrifuge and ultracentrifuge tubes. The pellet was resuspended in 50 µL of initial medium (PBS/ultraclean water/marine water). P3/IS, P4/IS, P11/IS, P12/IS, P16/IS, P21/IS, P26/IS Isolate from conditioned culture media of Phaeodactylum tricornutum microalgae. Culture of Phaeodactylum tricornutum CCAP 1052/1A from the Culture Collection of Algae and Protozoa (CCAP) of SAMS (Oban, Scotland) were grown in artificial seawater (Reef Crystals, Aquarium Systems, France). 22 g of salt was dissolved in one litre of distilled water, sterile filtered (0.2-micron cellulose filters, ref. 11107-47-CAN, Sartorius Stedim Biotech GmbH, Germany), autoclaved, and supplemented with Guillard’s (F/2) Marine Water Enrichment Solution (ref. G0154, Sigma Aldrich, USA)18. Cultures were grown in a respirometer (Echo, Slovenia) in 0.5-L borosilicate bottles, at 20 °C and 20 % illumination with a 14-hour light / 10-hour dark cycle, with aeration of 0.2 L/min. . EPs were isolated from a 10 mL sample by differential ultracentrifugation, The cells were removed by low-speed centrifugation (300 g, 10 min, 4°C, centrifuge Centric 260R with rotor RA 6/50 (Domel, Slovenia)), using 50 mL conical centrifuge tubes (ref. S.078.02.008.050, Isolab Laborgeräte GmbH, Germany); and 2000 g, 10 min, 4°C (Centric 400R centrifuge with rotor RS4/100 (Domel, Slovenia)), using 15 mL conical centrifuge tubes (ref. S.078.02.001.050, Isolab Laborgeräte GmbH, Germany). Each step was repeated twice. Then, the cell-depleted medium was centrifuged twice at 10 000 g and 4°C for 30 min (Beckman L8-70M ultracentrifuge, rotor SW55Ti (Beckman Coulter, USA)), using thin-wall polypropylene centrifuge tubes (ref. 326819, Beckman Coulter, USA) to remove larger cell debris. Finally, EPs were pelleted by ultracentrifugation at 118 000 g and 4°C, for 70 min in the same type of ultracentrifuge and ultracentrifuge tubes. The pellet was resuspended in 50 µL of marine water. P11/SN Supernatant from ultracentrifugation of Phaeodactylum tricornutum microalgae. Culture of Phaeodactylum tricornutum CCAP 1052/1A from the Culture Collection of Algae and Protozoa (CCAP) of SAMS (Oban, Scotland) were grown in artificial seawater (Reef Crystals, Aquarium Systems, France). 22 g of salt was dissolved in one litre of distilled water, sterile filtered (0.2-micron cellulose filters, ref. 11107-47-CAN, Sartorius Stedim Biotech GmbH, Germany), autoclaved, and supplemented with Guillard’s (F/2) Marine Water Enrichment Solution (ref. G0154, Sigma Aldrich, USA)18. Cultures were grown in a respirometer (Echo, Slovenia) in 0.5-L borosilicate bottles, at 20 °C and 20 % illumination with a 14-hour light / 10-hour dark cycle, with aeration of 0.2 L/min. . EPs were isolated from a 10 mL sample by differential ultracentrifugation, The cells were removed by low-speed centrifugation (300 g, 10 min, 4°C, centrifuge Centric 260R with rotor RA 6/50 (Domel, Slovenia)), using 50 mL conical centrifuge tubes (ref. S.078.02.008.050, Isolab Laborgeräte GmbH, Germany); and 2000 g, 10 min, 4°C (Centric 400R centrifuge with rotor RS4/100 (Domel, Slovenia)), using 15 mL conical centrifuge tubes (ref. S.078.02.001.050, Isolab Laborgeräte GmbH, Germany). Each step was repeated twice. Then, the cell-depleted medium was centrifuged twice at 10 000 g and 4°C for 30 min (Beckman L8-70M ultracentrifuge, rotor SW55Ti (Beckman Coulter, USA)), using 6 mL thin-wall polypropylene centrifuge tubes (ref. 326819, Beckman Coulter, USA) to remove larger cell debris. Finally, EPs were pelleted by ultracentrifugation at 118 000 g and 4°C, for 70 min in the same type of ultracentrifuge and ultracentrifuge tubes. Supernatant was collected to form P11/SN sample. LA-1000 liposomes diluted 1000x. The sample was prepared by mixing 25 weight % of soya granules (Fiorentini, Torino, Italy), 50% of ultraclean water and 25% of glycerol. The soyabean lecithin granules were placed into the falcon tubes. Water was added and the suspension was left at room temperature for 1 hour. Glycerol was added and the sample was mixed by pipetting with Pasteur pipette. The sample was diluted 1000x and filtered through 0.4 \(\mu \)mm filters. LB-1000 liposomes diluted 1000x. The sample was prepared by mixing 25 weight % of soya granules (Fiorentini, Torino, Italy), 50% of supernatant of isolation of EVs from spruce needle homogenate and 25% of glycerol. The soyabean lecithin granules were placed into the falcon tubes. Spruce supernatant was added and the suspension was left at room temperature for 1 hour. Glycerol was added and the sample was mixed by pipetting with Pasteur pipette. The sample was diluted 1000x and filtered through 0.4 \(\mu \)mm filters. LC-1000 Liposomes diluted 1000x. The sample was prepared by mixing equal weight % of soya granules (Fiorentini, Torino, Italy), supernatant of isolation of EVs from spruce needle homogenate and glycerol. Soyabean lecithin granules were placed into the falcon tube and glycerol was added. The sample was mixed by wortexing and supernatant of isolation of EVs from spruce needle homogenate was added. The sample was mixed by repetitive turning the falcon tube upside down. The sample was kept at room temperature for 6 months. The sample was diluted 1000x and filtered through 0.4 \(\mu \)mm filters. LA-100 liposomes diluted 100x. The sample was prepared by mixing 25 weight % of soya granules (Fiorentini, Torino, Italy), 50% of ultraclean water and 25% of glycerol. The soyabean lecithin granules were placed into the falcon tubes. Water was added and the suspension was left at room temperature for 1 hour. Glycerol was added and the sample was mixed by pipetting with Pasteur pipette. The sample was diluted 100x and filtered through0.4 \(\mu \)mm filters. LB-100 liposomes diluted 100x. The sample was prepared by mixing 25 weight % of soya granules (Fiorentini, Torino, Italy), 50% of supernatant of isolation of EVs from spruce needle homogenate and 25% of glycerol. The soyabean lecithin granules were placed into the falcon tubes. Spruce supernatant was added and the suspension was left at room temperature for 1 hour. Glycerol was added and the sample was mixed by pipetting with Pasteur pipette. The sample was diluted 100x and filtered through 0.4 \(\mu \)mm filters. LC-100 Liposomes diluted 100x. The sample was prepared by mixing equal weight % of soya granules (Fiorentini, Torino, Italy), supernatant of isolation of EVs from spruce needle homogenate and glycerol. Soyabean lecithin granules were placed into the falcon tube and glycerol was added. The sample was mixed by wortexing and supernatant of isolation of EVs from spruce needle homogenate was added. The sample was mixed by repetitive turning the falcon tube upside down. The sample was kept at room temperature for 6 months. The sample was diluted 100x and filtered through 0.4 \(\mu \)mm filters. &nbsp

The research presented herein follows an urgent global need for the development of novel surface engineering techniques that would allow the fabrication of next-generation cardiovascular stents, which would drastically reduce cardiovascular diseases (CVD). The combination of hydrothermal treatment (HT) and treatment with highly reactive oxygen plasma (P) allowed for the formation of an oxygen-rich nanostructured surface. The morphology, surface roughness, chemical composition and wettability of the newly prepared oxide layer on the Ti substrate were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) analysis. The alteration of surface characteristics influenced the material’s bio-performance platelet aggregation and activation was reduced on surfaces treated by hydrothermal treatment, as well as after plasma treatment. Moreover, it was shown that surfaces treated by both treatment procedures (HT and P) promoted the adhesion and proliferation of vascular endothelial cells, while at the same time inhibiting the adhesion and proliferation of vascular smooth muscle cells. The combination of both techniques presents a novel approach for the fabrication of vascular implants, with superior characteristics.

Within the micro and nano world, tiny membrane-enclosed bits of material are more or less free to move and act as communication tools within cells, between cells, between different tissues and between organisms in global environment. Based on the mechanism of membrane budding and vesiculation that includes all types of cells, in this review, we attempted to present a review on SARS-CoV-2 virus actions in compartments of different scales (cells and their surroundings, tissues, organisms and society). Interactions of the virus with cells on a molecular level, with neural system, endothelium, hematopoietic system, gastrointestinal system and genitourinary system. Transmission route between organisms and between mother and fetus are considered. Also, transmission of virus through contact with materials and with environment, the suggested measures to prevent contamination with the virus and to support the organism against the disease are given.

ObjectivesPeri-implantitis and peri-mucositis pose a severe threat to the success of dental implants. Current research focuses on the development of surfaces that inhibit biofilm formation while not inferring with tissue integration. This study compared the adherence of two oral bacterial species, Streptococcus sanguinis and Streptococcus mutans to nanostructured titanium surfaces.MethodsThe samples included TiO2 nanotubes formed by anodization of titanium foil of 100, 50 and 15nm diameter (NT15, NT50, NT100), a nanoporous (15nm pore diameter) surface and compact TiO2 control. Adherent surviving bacteria were enumerated after 1h in an artificial saliva medium containing bovine mucin.ResultsLowest numbers of adherent bacteria of both species were recovered from the original titanium foil and nanoporous surface and highest numbers from the Ti100 nanotubes. Numbers of attached S. sanguinis increased in the order (NT15

In the present study we demonstrated that composite PPHMDS/DND coatings with elastic moduli close to those of mature bone tissue (0.2-2.8 GPa) stimulated growth and osteogenic differentiation of human adipose-derived mesenchymal stem cells (hAD-MSCs). Composite coatings were prepared by a method of plasma polymerization (PP) where detonation nanodiamond (DND) particles in different amounts (0.1, 0.5, and 1 mg/mL) were added to hexamethyldisiloxane (HMDS) before plasma deposition. This method allows variation only in the reduced elastic modulus (Er') with increase in the particle concentration, while the other surface properties, including surface wettability and topography, did not change. The response of hAD-MSCs to the increasing stiffness showed an effect on adhesion and osteogenic differentiation but not on cell proliferation. Matrix mineralization and cell spreading were maximized on PPHMDS/DND coatings with the highest elastic modulus (2.826 GPa), while the differences in proliferation rates among the samples were negligible. In general, PPHMDS/DND coatings provide better conditions for growth and osteogenic differentiation of hAD-MSCs in comparison to glass coverslips, confirming their suitability for osteo-integration applications. Additionally, our findings support the hypothesis that biomaterials with elasticity similar to that of the native tissue can improve the differentiation potential of mesenchymal stem cells.

Membrane budding often leads to the formation and release of microvesicles. The latter might play an important role in long distance cell-to-cell communication, owing to their ability to move with body fluids. Several mechanisms exist which might trigger the pinching off of globular buds from the parent membrane (vesiculation). In this paper, we consider the theoretical impacts of topological defects (frustrations) on this process in the membranes that exhibit global in-plane orientational order. A Landau–de Gennes theoretical approach is used in terms of tensor orientational order parameters. The impact of membrane shapes on position and the number of defects is analyzed. In studied cases, only defects with winding numbers m = ±1/2 appear, where we refer to the number of defects with m = 1/2 as defects, and with m = –1/2 as anti-defects. It is demonstrated that defects are attracted to regions with maximal positive Gaussian curvature, K. On the contrary, anti-defects are attracted to membrane regions exhibiting minimal negative values of K. We show on membrane structures exhibiting spherical topology that the coexistence of regions with K > 0 and K < 0 might trigger formation of defect–anti-defect pairs for strong enough local membrane curvatures. Critical conditions for triggering pairs are determined in several demonstrative cases. Then the additionally appeared anti-defects are assembled at the membrane neck, where K < 0. Consequent strong local fluctuations of membrane constituent anisotropic molecules might trigger membrane fission neck rupture, enabling a membrane fission process and the release of membrane daughter microvesicles (ie, vesiculation).

Effectively, two-dimensional (2D) closed films exhibiting in-plane orientational ordering (ordered shells) might be instrumental for the realization of scaled crystals. In them, ordered shells are expected to play the role of atoms. Furthermore, topological defects (TDs) within them would determine their valence. Namely, bonding among shells within an isotropic liquid matrix could be established via appropriate nano-binders (i.e., linkers) which tend to be attached to the cores of TDs exploiting the defect core replacement mechanism. Consequently, by varying configurations of TDs one could nucleate growth of scaled crystals displaying different symmetries. For this purpose, it is of interest to develop a simple and robust mechanism via which one could control the position and number of TDs in such atoms. In this paper, we use a minimal mesoscopic model, where variational parameters are the 2D curvature tensor and the 2D orientational tensor order parameter. We demonstrate numerically the efficiency of the effective topological defect cancellation mechanism to predict positional assembling of TDs in ordered films characterized by spatially nonhomogeneous Gaussian curvature. Furthermore, we show how one could efficiently switch among qualitatively different structures by using a relative volume v of ordered shells, which represents a relatively simple naturally accessible control parameter.

Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy.

We studied biological membranes of spherical topology within the framework of the spontaneous curvature model. Both Monte Carlo simulations and the numerical minimization of the curvature energy were used to obtain the shapes of the vesicles. The shapes of the vesicles and their energy were calculated for different values of the reduced volume. The vesicles which exhibit inplane ordering were also studied. Minimal models have been developed in order to study the orientational ordering in colloids coated with a thin sheet of nematic liquid crystal (nematic shells).The topological defects are always present on the surfaces with the topology of a sphere.The location of the topological defects depends strongly on the curvature of the surface. We studied the nematic ordering and the formation of topological defects on vesicles obtained by the minimization of the spontaneous curvature energy.

Acta of Bioengineering and Biomechanics; 04/2017; ISSN 1509-409X

The biomechanical role of the horseshoe geometry of the acetabular cartilage is described using a three-dimensional mathematical model. It is shown that the acetabular fossa contributes to a more uniform articular contact stress distribution and a consequent decrease in the peak contact stress. Based on the results it is suggested that the characteristic horseshoe shape of the articular cartilage in the human acetabulum optimizes the contact stress distribution in the hip joint.

Membrane, tanke lonice med dvema področjema, so lahko podvržene termičnim fluktuacijam. Pomemben primer tankih mejnih plasti v naravi so membrane v bioloških celicah. Celice različnih velikosti, oblik in funkcij so osnovni sestavni deli bioloških sistemov. Kljub raznolikosti celic, ki jih najdemo v bioloških sistemih, so osnovni gradniki in njihova kemijska sestava večine celic enaki. Lastnosti bioloških membran, ki obdajajo celice ali njene organele, se precej razlikujejo od lastnosti makroskopskih objektov, ki smo jih vajeni iz vsakodnevnega življenja. Na primer, lipidna dvojna plast, osnova bioloških membran, je tako mehka na upogib, da lahko že termično gibanje okolne raztopine pri sobni temperaturi povzroča spremembe oblike membrane. S spektralno analizo takšnih terminih fluktuacij biološke membrane je mogoče neinvazivno določati njene mehanske lastnosti. Migetanje (utripanje) rdečih krvnih celic je zaznal že Browicz v poznem 19. stoletju z uporabo optičnega mikroskopa. Danes lahko fluktuacije lipidne dvojne plasti opazujemo z izboljšanim faznokontrastnim mikroskopom ter s spektralno analizo teh fluktuacij neinvazivno merimo nekatere ključne lastnosti bioloških celic. V doktorski disertaciji smo izdelali merilni sistem za analizo termičnih fluktuacij bioloških membran s faznokontrastnim mikroskopom. Končni cilj tega razvoja je celostno računalniško krmiljeno eksperimentalno okolje primerno za raziskovalce s področja bioloških znanosti. V doktorskem delu smo predstavili tudi posodobljen in izboljšan računalniki program za simulacije Monte Carlo z naključnimi trikotniškimi mrežami, s katerimi je mogoče modelirati termine fluktuacije bioloških membran. S simulacijami Monte-Carlo smo preverili nekatere predpostavke teoretičnega modela za določanje elastinih lastnosti bioloških membran z analizo njihovih terminih fluktuacij. Teoretični model Milnerja in Safrana za določanje elastinih lastnosti bioloških membran z analizo njihovih terminih fluktuacij temelji na znanem Helfrichovem modelu membrane in vsebuje tudi implicitno predpostavko, da pri terminih fluktuacijah lipidne dvojne plasti nihanji upogiba in natega membrane nista sklopljeni in lahko uporabimo približek povprečnega polja. Veljavnost zgornje predpostavke nameravamo preveriti z numerinim modelom. S simulacijami Monte Carlo z naključnimi trikotniškimi mrežami lahko modeliramo biološke membrane v njihovem termodinamičnem ravnovesju in stohastični Metropolis Hastingsov algoritem nam omogoča analizo njihovih termičnih fluktuacij. Čeprav nam tudi nekateri drugih numerični modeli membrane nudijo primerno časovno zahtevnost za obravnavo celotne celice oziroma lipidnega mehurka, so pri simulacijah Monte Carlo z naključnimi trikotniškimi mrežami elastine konstante membrane (npr. upogibna konstanta) sestavni del samega modela. Čas izvajanja simulacij Monte Carlo z naključnimi trikotniškimi mrežamise povečuje z večanjem simuliranega sistema. Časovna zahtevnost simulacije narašča s kvadratom števila vozlišče naključne trikotniške mreže, če upoštevamo interakcije dolgega dosega med vozlišči, kot so na primer elektrostatične sile med naelektrenimi delci membrane. Ker število vozlišče še dodatno narašča s kvadratom radija celice, simulacijski čas torej narašča s četrto potenco premera celice. S skaliranjem sistema lahko delno rešimo problem časovne zahtevnosti, če lahko majhne površine membrane, ki jo sestavlja množica elementov (molekul) opišemo z enim vozliščem v trikotniški mreži. Dodatno pohitritev simulacij lahko dosežemo s paralelizacijo simulacijskega algoritma in tako izkoristimo prednosti, ki jih nudijo novodobne večjedrne in večnitne procesorske arhitekture. Raziskali smo možnosti paralelizacije naših simulacij z naključnimi trikotniškimi mrežami s pomočjo različnih paralelizacijskih pristopov. Sistemi, ki temeljijo na metodah merjenja s faznokontrastnim mikroskopom, reflektivno interferenčnim in s fluorescentno interferenčnim mikroskopom so primeri merilnih sistemov, ki omogočajo neinvazivno določitev elastičnih lastnosti membran. Sistem je sestavljen iz faznokontrastnega mikroskopa, stroboskopske osvetlitve in kamere povezane z računalnikom. Kamera in stroboskopska osvetlitev morata biti ustrezno sinhronizirana, da lahko natančno zabeležimo obliko membrane v danem času. Stroboskop kratkotrajno osvetli vzorec znotraj posameznega zajema slike in tako odpravi problem neostre slike zaradi hitrih fluktuacij, ki bi sliko zameglile, če bi dopustili daljši čas osvetlitve med integracijskim časom kamere. Stroboskop lahko pri razelektritvi skozi stroboskopsko luč povzroči mehanske tresljaje celotnega mikroskopa in s tem tudi merjenca. Tresljaji pozročajo neželjene premike in deformacije membran, hkrati pa pripomorejo k manjši ločljivosti zaznave robov. Prednost izvedenega merilnega sistema je v popolni avtomatizaciji meritev in izboljšanem sistemu za osvetlitev vzorca. Membranes, thin barriers between compartments, can uctuate. An important example in nature are membranes of biological cells. Cells, these building blocks of biological systems, have diverse capabilities and shapes. However, the basic structural elements and their chemical composition of most cells are the same. Fluid sheets (membranes) enclose the cell and its compartments, while networks of fillaments, if present, maintain the cell's shape and help organize its contents. These structural elements can have quite di_erent mechanical properties than macroscopic objects of our everyday life. For example, they are very soft solely thermal uctuations at room temperature can generate gentle undulations of membranes.Flickering" of red blood cells was already recorded in the late 19th century by Browicz using the light microscope. Today, with phase-contrast microscopy, non-invasive spectral analysis of those thermal uctuations of biological membranes can provide useful information of the membrane properties.Theoretical model for determining elastic properties of biological membranes with analysis of thermal uctuations by Milner and Safran is based on Helfrich model of membrane and includes also an implicit assumption that in the thermal uctuations of phospholipid bilayers, the shape uctuation modes are not correlated with the lateral stretching modes and that the mean-field approximation can be used. Using Randomly triangulated surfaces, we can simulate biological membrane systems in their thermodynamical equilibrium, where the stochastic Metropolis-Hastings algorithm allows us to sample their thermal uctuations. In this thesis, the coarse-grained model of the membrane is implemented in the program written in C programming language, where the membrane is represented by randomly triangulated network. The model takes into account the assumptions by Milner and Safran. The output of the simulator is the bending sti_ness of the membrane Kc which can be compared with the input bending stiffness , to verify if the numerical simulations are in accordance with the theoretical predictions of Milner and Safran. The randomly triangulated surfaces Monte-Carlo simulations can become time consuming for large systems, therefore some sort of parallelization is needed to harvest the capabilities of modern computers. Two approaches were made and compared. The problem proved to be embarrassingly parallelizable and we measured near theoretical max. speedup of the simulations by running multiple instances of the simulators and combining their statistics. Systems based on method of measurement of thermal uctuations with phase-contrast microscopy, interference contrast microscopy and uorescent-interference contrast microscopyare examples of non-invasive determination of the elastic properties of membranes. Our system is based on phase-contrast microscope and illumination apparatus presented in and, including image analysis described in. It basically consists of a phase-contrast microscope, a stroboscopic lighting system and a camera, connected to a computer. The camera and the lighting system was synchronized to allow a precise, blur-less registration of the membrane shape at the given moment, which is then analysed using user friendly software on the computer. The results of the simulations con_rmed the assumptions of Milner and Safran. The measurements of the simulations were behaving accordingly to the prediction of the equation of Milner and Safran, thus we concluded that the numerical simulations of nearly spherical vesicles modelled with triangulated networks can be used to determine the bending sti_- ness. Depending on the resolution of the simulations (the density of the mesh) the di_erence between input and measured bending sti_ness can be well below 10%.