Cellulose Tubes Research Articles

Tissue-engineered cellulose tubes for microvascular and lymphatic reconstruction: A translational and feasibility study

BackgroundLymphedema microsurgery is an emerging treatment modality, with dissimilar long-term outcomes. One of the main technical challenges in lymphatic microsurgery is the identification and availability of suitable donor vessels for anastomosis. Tissue engineering using biomaterials has shown promise in addressing vessel quality issues in other fields, but its application in microsurgery is still limited. MethodsDecellularized cellulose tubes were developed and bioengineered by decellularizing stems of Taraxacum-Ruderalia. The microscopic structure, mechanical properties, and remnant DNA content of the cellulose tubes were evaluated. Human and murine skin fibroblasts and dermal lymphatic endothelial cells were isolated and cultured for recellularization studies. Biocompatibility, proliferative capacity, and ex-vivo endothelialization of the cellulose tubes were assessed as potential interposition grafts. Finally, the engineered cellulose tubes were assessed as interposing xenografts for LVA in an ex-vivo swine limb model. ResultsThe decellularized cellulose tubes exhibited a suitable microscopic structure, mechanical properties, and low remnant DNA content. The tubes showed adequate biocompatibility, supported cell proliferation, and facilitated spontaneous ex-vivo endothelialization of lymphatic endothelial cells. In the swine limb model, LVA using the engineered cellulose tubes was successfully performed. ConclusionThis translational study presents the use of decellularized cellulose tubes as an adjunct for micro and supermicrosurgical reconstruction. The developed tubes demonstrated favorable structural, mechanical, and biocompatible properties, making them a potential candidate for improving long-term outcomes in lymphedema surgical treatment. The next translational step would be trialing the obtained tubes in a microsurgical in-vivo model.

Real-Time Quantitative Evaluation of a Drug during Liposome Preparation Using a Probe-Type Raman Spectrometer.

During the manufacturing process of liposome formulations, it is considered difficult to evaluate their physicochemical properties and biological profiles due to the complexity of their structure and manufacturing process. Conventional quality evaluation is labor-intensive and time-consuming; therefore, there was a need to introduce a method that could perform in-line, real-time evaluation during the manufacturing process. In this study, Raman spectroscopy was used to monitor in real time the encapsulation of drugs into liposomes and the drug release, which are particularly important quality evaluation items. Furthermore, Raman spectroscopy combined with partial least-squares (PLS) analysis was used for quantitative drug evaluation to assess consistency with results from UV-visible spectrophotometry (UV), a common quantification method. The prepared various ciprofloxacin (CPFX) liposomes were placed in cellulose tubes, and a probe-type Raman spectrophotometer was used to monitor drug encapsulation, the removal of unencapsulated drug, and drug release characteristics in real time using a dialysis method. In the Raman spectra of the liposomes prepared by remote loading, the intensities of the CPFX-derived peaks increased upon drug encapsulation and showed a slight decrease upon removal of the unencapsulated drug. Furthermore, the peak intensity decreased more gradually during the drug release. In all Raman monitoring experiments, the discrepancy between quantified values of CPFX concentration in liposomes, as measured by Raman spectroscopy combined with partial least-squares (PLS) analysis, and those obtained through ultraviolet (UV) spectrophotometry was within 6.7%. The results revealed that the quantitative evaluation of drugs using a combination of Raman spectroscopy and PLS analysis was as accurate as the evaluation using UV spectrophotometry, which was used for comparison. These results indicate the promising potential of Raman spectroscopy as an innovative method for the quality evaluation of liposomal formulations.

Full biomass-derived multifunctional aerogel for solar-driven interfacial evaporation

Developing high-efficient utilization of thermal energy, excellent water transport path and mechanical stablility of biochar based solar-driven interfacial evaporator (SDIE) is critical for but still challenge. Herein, a three-dimensional network of porous scaffolds aerogel is prepared by cross-linking hydrophilic plantain cellulose (PC) and biomass hollow carbon tubes (HCTs) with excellent photothermal properties. The HCTs and PC winding with each other, the water adsorption by PC and desorption by HCTs which improve water evaporation. Under 1.0 sun illumination, the optimized PC@HCTs aerogel temperature on gas-liquid interface rapidly reach to 46.7 °C and the evaporation rate is 1.86 kg m−2h−1. In addition, PC@HCTs aerogel possess excellent water evaporation under high concentration of salt solutions and salt tolerance ability. Moreover, the PC@HCTs aerogel has obvious purification effect for seawater, heavy metal ion solution, oil-water emulsion and organic dye wastewater. Importantly, the dry PC@HCTs possesses excellent hardness while hyperelasticity in water. More importantly, the PC@HCTs aerogel with green recyclability which change the growth environment of sand and plants healthier, thus take materials from nature and final regress to nature. This work has the great scientific significance to promote the actual use of biochar based solar steam evaporators.

RDX Red Gum: A High Performance Pressable Formulation

ABSTRACT Explosive pellets containing binary mixtures of 1,3,5-trinitro-1,3,5-triazine (RDX) and yacca resin “red gum” (RG) with composition ratios of 90:10, 95:5, and 98:2 RDX:RG were prepared. These were created without use of specialized pressing or casting facilities, making it a convenient formulation for researchers. Red gum, a component of molding powder, was mixed with RDX, both in powder form and in slurry format. The addition of red gum to RDX did not significantly change the sensitivity of RDX to impact or friction nor was thermal stability dramatically altered as judged by differential scanning calorimetry (DSC). Formulations of RDX:RG were pressed to produce pellets with densities ranging from 1.628-1.683 g/cm3. Pressed pellets were assembled in clear cellulose tubes to allow high speed camera photography to assess detonation velocity. Velocities between 8.04-8.50 km/s were determined. Photon Doppler velocimetry (PDV) measured CJ-pressures in the pellets between 24-29 GPa.

Investigating the Performance of Solar Steam Generation Using a Carbonized Cotton-Based Evaporator

Solar-driven steam generation as a potential green technology has attracted extensive attention to solve the freshwater scarcity crisis. Photothermal materials as the key section of solar steam generation have been widely reported. However, there is still a challenge in developing easily prepared, environmental-friendly, and low-cost materials. Herein, the simple, scalable, and porous carbonized cotton was prepared as an evaporator to enhance solar-based evaporation, which has excellent light absorption ability in the range of the full spectrum (300–2,500 nm). Benefiting from 95% solar absorption and the pores between the cellulose tubes, the carbonized cotton heated by plate carbonization reaches a steam generation rate of 0.8 kg m−2 h−1, which is about 5 times that of untreated cotton. Compared with tube furnace carbonization, flat plate heating carbonization of cotton requires lower equipment requirements and does not need nitrogen protection and cleaning tar, and the photothermal conversion efficiencies of both are similar. In addition, carbonized cotton as an evaporator was heated up rapidly under 1 sun irradiation and reached a stable temperature in 20 s, greatly improving the photothermal conversion rate. Therefore, plate heating carbonized cotton provides a good idea for preparing solar photothermal conversion materials and a novel strategy for simplifying the production of biomass thermal evaporators.

Reduced Pressure Drop in Viscoelastic Polydimethylsiloxane Wall Channels.

Polydimethylsiloxane (PDMS) is an important viscoelastic material that finds applications in a large number of engineering systems, particularly lab-on-chip microfluidic devices built with a flexible substrate. Channels made of PDMS, used for transporting analytes, are integral to these applications. The PDMS viscoelastic nature can induce additional hydrodynamic contributions at the soft wall/fluid interface compared to rigid walls. In this research, we investigated the pressure drop within PDMS channels bounded by rigid tubes (cellulose tubes). The bulging effect of the PDMS was limited by the rigid tubes under flowing fluids. The PDMS viscoelasticity was modulated by changing the ratio of the base to the cross-linker from 10:1 to 35:1. We observed that the pressure drop of the flowing fluids within the channel decreased with the increased loss tangent of the PDMS in the examined laminar regime [Reynolds number (Re) ∼ 23-58.6 for water and Re ∼ 0.69-8.69 for glycerol solution]. The elastic PDMS 10:1 wall channels followed the classical Hagen Poiseuille's equation, but the PDMS walls with lower cross-linker concentrations and thicker walls decreased pressure drops. The friction factor (f) for the PDMS channels with the two working fluids could be approximated as f = 47/Re. We provide a correlation between the pressure drop and PDMS viscoelasticity based on experimental findings. In the correlation, the loss tangent predominates; the larger the loss tangent, the smaller is the pressure drop. The research findings appear to be unexpected if only considering the energy dissipation of viscoelastic PDMS walls. We attributed the reduction in the pressure drop to a lubricating effect of the viscoelastic PDMS walls in the presence of the working fluids. Our results reveal the importance of the subtle diffusion of the residual oligomers and water from the bulk to the soft wall/fluid interface for the observed pressure drop in soft wall channels.

Production of bacterial cellulose tubes for biomedical applications: Analysis of the effect of fermentation time on selected properties

Biosynthesis of bacterial cellulose (BC) in cylindrical oxygen permeable molds allows the production of hollow tubular structures of increasing interest for biomedical applications (artificial blood vessels, ureters, urethra, trachea, esophagus, etc.). In the current contribution a simple set-up is used to obtain BC tubes of predefined dimensions; and the effects of fermentation time on the water holding capacity, nanofibrils network architecture, specific surface area, chemical purity, thermal stability, mechanical properties, and cell adhesion, proliferation and migration of BC tubes are systematically analysed for the first time. The results reported highlight the role of culture time on key properties of the BC tubes produced, with significant differences arising from the denser and more compact fibril arrangements generated at longer fermentation intervals.

Construction of porous cellulose tubes and the evaluations of mechanical properties and cytocompatibility

AbstractIn this work, regenerated cellulose (RC) tubes with the porous structure were successfully fabricated for constructing the non‐invasive detection platform of vascular microenvironment. Polyethylene oxide (PEO) as a porogen was applied to induce porous structure of cellulose tubes. Tensile and burst pressure tests were carried out to evaluate the effects of PEO molecular weight and amount on the mechanical properties of cellulose tubes. The results showed that tensile strength of RC tubes was increased with increasing PEO molecular weight. The compliance of cellulose tubes decreased with increasing the PEO content. When 120 kDa PEO was applied, the average tensile strength of RC tubes could reach 1.27 MPa. The maximum burst pressure and compliance of RC tubes could reach 488.25 ± 35 mmHg and 7.50 ± 3.7%/100 mmHg, respectively. Human umbilical vein endothelia cells (HUVECs) exhibited obvious proliferation on cellulose tubes, and the collagen coating further improve the biocompatibility. The incorporated collagen further improved adhesion of the cells and growth on cellulose tubes. This work provided a kind of cellulose‐based tube material with potential application for the construction of the vitro vascular microenvironment.

Production and evaluation of biosynthesized cellulose tubes as promising nerve guides for spinal cord injury treatment.

Spinal cord injury (SCI) is a central nervous disorder that can result in permanent motor and sensory damage due to a severed communication pathway. Although there is currently no effective treatment, nerve guide tubes have been used to bridge the injured stumps and act as drug delivery systems. In this study, biosynthesized cellulose (BC) nerve guides were prepared, and nerve growth factor (NGF)-a model growth factor-was incorporated into the tubular nerve guide in order to obtain a nerve guide/drug delivery system to assist the regeneration. To achieve this, Gluconacetobacter hansenii was cultivated in a special bioreactor to produce biosynthesized cellulose tubes (BCTs) in situ, and the physical and mechanical properties of the BCTs obtained from different cultivation time points were evaluated. Our results showed that the properties of the BCTs were comparable to those of the native human neural tissues, and that the NGF released from the BCTs was bioactive for at least 7 days as evaluated by PC12 cell cultures in vitro. In summary, this study evaluated the use of BCT as a drug releasing nerve guide, and our results showed that the BCT is an attractive strategy to enhance nerve regeneration after the SCI.

Microbes Culture System Using Cellulose Tubes and Photocatalyst-Coated Glass Balls.

Currently, microbes are utilized in many fields, such as medicine, food and environment etc. For more application of microbes, we need a new culture system, which can culture target microbes in large quantities at low cost. Thereupon, we propose a culture system using cellulose tubes. Target microbes are encapsulated inside the cellulose tubes, where they acquire nutrients and oxygen through nano pores of the tubes and are protected from competitive microbes even in open environment. To further increase the amount of oxygen and nutritions available for the target microbes, we propose photocatalyst-coated glass balls (PCGB) to sterilize competing microbes outside the tubes. We experimentally verified the effectiveness of the proposed culture system by culturing Coryne gultamicum as the target microbes.

Design and Characterization of an Acoustically and Structurally Matched 3-D-Printed Model for Transcranial Ultrasound Imaging.

For investigating human transcranial ultrasound imaging (TUI) through the temporal bone, an intact human skull is needed. Since it is complex and expensive to obtain one, it requires that experiments are performed without excision or abrasion of the skull. Besides, to mimic blood circulation for the vessel target, cellulose tubes generally fit the vessel simulation with straight linear features. These issues, which limit experimental studies, can be overcome by designing a 3-D-printed skull model with acoustic and dimensional properties that match a real skull and a vessel model with curve and bifurcation. First, the optimal printing material which matched a real skull in terms of the acoustic attenuation coefficient and sound propagation velocity was identified at 2-MHz frequency, i.e., 7.06 dB/mm and 2168.71 m/s for the skull while 6.98 dB/mm and 2114.72 m/s for the printed material, respectively. After modeling, the average thickness of the temporal bone in the printed skull was about 1.8 mm, while it was to 1.7 mm in the real skull. Then, a vascular phantom was designed with 3-D-printed vessels of low acoustic attenuation (0.6 dB/mm). It was covered with a porcine brain tissue contained within a transparent polyacrylamide gel. After characterizing the acoustic consistency, based on the designed skull model and vascular phantom, vessels with inner diameters of 1 and 0.7 mm were distinguished by resolution enhanced imaging with low frequency. Measurements and imaging results proved that the model and phantom are authentic and viable alternatives, and will be of interest for TUI, high intensity focused ultrasound, or other therapy studies.

Quantitative analysis of the angiogenic microvasculature in tumor using multiple scattering and dual-frequency transducers

The objective is to characterize angiogenic networks using contrast-enhanced multiple scattering. The methods relies on the measurement of the diffusion constant from the time evolution of the incoherent backscattered intensity. Dual-frequency arrays allow to emit a pulse at a frequency close to resonance frequency of microbubbles, and to receive the backscattered echoes at higher harmonics, resulting in better contrast-to-tissue ratio compared to single frequency transducers. At 8 MHz, we demonstrated that the diffusion constant enables the quantification of the vascular density and anisotropy in tumor-related vasculature in rat models in vivo. We show here that the results could be further improved using a dual-frequency approach, using two linear arrays with different central frequencies (7 MHz/18 MHz) and using a custom made dual frequency transducer (3 MHz/15 MHz). The minimum detectable distance between two vessel-mimicking cellulose tubes filled with contrast agents was measured via the diffusion constant. The dual-frequency approach drastically reduced the smallest detectable distance between tubes, which was found to be 25µm using a single frequency, 20µm using two linear arrays and 10µm using the custom dual-frequency array, respectively. These results show that measuring the diffusion constant with a dual frequency array can enable the quantification of vessel density with high accuracy

Improvement of microbial culture using cellulose tubes by photocatalyst and iodine balls

Improvement of microbial culture using cellulose tubes by photocatalyst and iodine balls

– New methods Modified bacterial cellulose tubes for regeneration of damaged peripheral nerves

IntroductionThe subject of the experiment was bacterial nanocellulose, a natural polymer produced by bacteria – Gluconacetobacter xylinus. Following a specific modification process a cartilage-like material for restoration of damaged tissues may be produced. The obtained implants with excellent biocompatibility, mouldability, biophysical and chemical properties perfectly fit the needs of reconstructive surgery. The goal of the experiment was to develop and analyze cellulosic guidance channels in vivo for the reconstruction of damaged peripheral nerves.Material and methodsThe experiments were conducted on Wistar rats, femoral nerve. Cellulose was produced according to a self-patented method. In the experimental group tubulization was applied, whereas in the control traditional end-to-end connection was used. Observation time was 30, 60, 90, and 180 days. Results evaluation included histological analysis and postoperative observation of motor recovery.ResultsThe overgrowth of connective tissue and disorganisation of neural structures was evident in 86.67% of control specimens, while for cellulosic group it was only 35% (p = 0.0022). Tubulization prevented the excessive proliferation of connective tissue and isolated from penetration with scar tissue. Autocannibalism, being probably an evidence of neurotrophic factors amassment, was observed in cellulosic group but not in the control one. Motor recovery did not differ significantly (p > 0.05). Biocompatibility of implants was affirmed by very small level of tissue response and susceptibility to vascularisation.ConclusionsCellulosic neurotubes effectively prevent the formation of neuromas. They are of very good biocompatibility and allow the accumulation of neurotrophic factors inside, thus facilitating the process of nerve regeneration.

Studies on the biocompatibility of bacterial cellulose

Bacterial cellulose was functionalized with a chimeric protein containing a cellulose-binding module and the adhesion peptide Arg-Gly-Asp. Small-diameter bacterial cellulose membranes were produced and subcutaneously implanted in sheep for 1–32 weeks. The implants triggered a biological response similar to other high surface-to-volume implants. There were no significant differences in the inflammation degree between the bacterial cellulose coated with the recombinant protein Arg-Gly-Asp–cellulose-binding module and the native bacterial cellulose. The implants were considered to be mildly irritating to the tissue compared to the negative control sample (expanded polytetrafluoroethylene). The analysis of the fluorescence microscopy revealed that, apart from increasing cell adhesion, the presence of Arg-Gly-Asp stimulated an even cell distribution, while the cells on the untreated bacterial cellulose seemed to form aggregates. Furthermore, the cells on the Arg-Gly-Asp–treated bacterial cellulose presented a more elongated morphology. Mechanical tests indicated that the small-diameter bacterial cellulose tubes were more elastic than the human arteries and veins.

A sensitive TLRH targeted imaging technique for ultrasonic molecular imaging

The primary goals of ultrasound molecular imaging are the detection and imaging of ultrasound contrast agents (microbubbles), which are bound to specific vascular surface receptors. Imaging methods that can sensitively and selectively detect and distinguish bound microbubbles from freely circulating microbubbles (free microbubbles) and surrounding tissue are critically important for the practical application of ultrasound contrast molecular imaging. Microbubbles excited by low-frequency acoustic pulses emit wide-band echoes with a bandwidth extending beyond 20 MHz; we refer to this technique as transmission at a low frequency and reception at a high frequency (TLRH). Using this wideband, transient echo, we have developed and implemented a targeted imaging technique incorporating a multifrequency colinear array and the Siemens Antares imaging system. The multifrequency colinear array integrates a center 5.4-MHz array, used to receive echoes and produce radiation force, and 2 outer 1.5-MHz arrays used to transmit low-frequency incident pulses. The targeted imaging technique makes use of an acoustic radiation force subsequence to enhance accumulation and a TLRH imaging subsequence to detect bound microbubbles. The radiofrequency (RF) data obtained from the TLRH imaging subsequence are processed to separate echo signatures between tissue, free microbubbles, and bound microbubbles. By imaging biotin-coated microbubbles targeted to avidin-coated cellulose tubes, we demonstrate that the proposed method has a high contrast-to-tissue ratio (up to 34 dB) and a high sensitivity to bound microbubbles (with the ratio of echoes from bound microbubbles versus free microbubbles extending up to 23 dB). The effects of the imaging pulse acoustic pressure, the radiation force subsequence, and the use of various slow-time filters on the targeted imaging quality are studied. The TLRH targeted imaging method is demonstrated in this study to provide sensitive and selective detection of bound microbubbles for ultrasound molecularly targeted imaging.

동절기 자연수계 환경에 노출된 크립토스포리디움의 활성 및 감염성 변화

This study was designed to establish the time frame of viability and infectivity of Cryptosporidium, when the Cryptosporidium is discharged to the aquatic environment. Changes in viability and infectivity of Cryptosporidium in relation to temperature and pH were investigated during winter (Dec 05-Feb 06) using semipermeable cellulose tubes containing infective Cryptosporidium. Infectivity was maintained at 50% after 30 days and almost completely lost after 50 days. It was also established that viability was maintained at about 8% after 90 days.

Transmitted Ultrasound Pressure Variation in Micro Blood Vessel Phantoms

Silica, cellulose and polymethylmethacrylate tubes with inner diameters of ten to a few hundred microns are commonly used as blood vessel phantoms in in vitro studies of microbubble or nanodroplet behavior during insonation. However, a detailed investigation of the ultrasonic fields within these micro-tubes has not yet been performed. This work provides a theoretical analysis of the ultrasonic fields within micro-tubes. Numerical results show that for the same tube material, the interaction between the micro-tube and megaHertz-frequency ultrasound may vary drastically with incident frequency, tube diameter and wall thickness. For 10 MHz ultrasonic insonation of a polymethylmethacrylate (PMMA) tube with an inner diameter of 195 μm and an outer diameter of 260 μm, the peak pressure within the tube can be up to 300% of incident pressure amplitude. However, using 1 MHz ultrasound and a silica tube with an inner diameter of 12 μm and an outer diameter of 50 μm, the peak pressure within the tube is only 12% of the incident pressure amplitude and correspondingly, the spatial-average-time-average intensity within the tube is only 1% of the incident intensity. (E-mail: spqin@ucdavis.edu)

Influence of cultivation conditions on mechanical and morphological properties of bacterial cellulose tubes

Bacterial cellulose (BC) was deposited in tubular form by fermenting Acetobacter xylinum on top of silicone tubes as an oxygenated support and by blowing different concentrations of oxygen, that is, 21% (air), 35%, 50%, and 100%. Mechanical properties such as burst pressure and tensile properties were evaluated for all tubes. The burst pressure of the tubes increased with an increase in oxygen ratio and reached a top value of 880 mmHg at 100% oxygen. The Young's modulus was approximately 5 MPa for all tubes, irrespective of the oxygen ratio. The elongation to break decreased from 30% to 10-20% when the oxygen ratio was increased. The morphology of the tubes was characterized by Scanning Electron Microscopy (SEM). All tubes had an even inner side and a more porous outer side. The cross section indicated that the tubes are composed of layers and that the amount of layers and the yield of cellulose increased with an increase in oxygen ratio. We propose that an internal vessel wall with high density is required for the tube to sustain a certain pressure. An increase in wall thickness by an increase in oxygen ratio might explain the increasing burst pressure with increasing oxygen ratio. The fermentation method used renders it possible to produce branched tubes, tubes with unlimited length and inner diameters. Endothelial cells (ECs) were grown onto the lumen of the tubes. The cells formed a confluent layer after 7 days. The tubes potential as a vascular graft is currently under investigation in a large animal model at the Centre of Vascular Engineering, Sahlgrenska University

High-pressure freezing and freeze substitution of gravid Caenorhabditis elegans (Nematoda: Rhabditida) for transmission electron microscopy

Abstract Because chemical fixatives have a profound negative influence on tissue morphology and antigenicity, alternative fixation methods must be applied for some purposes. In this work we used high-pressure freezing (HPF) followed by freeze substitution to maximally preserve antigenicity and morphology. We developed a pipette method for bringing living Caenorhabditis elegans nematodes into the HPF recipient. Using cellulose tubes, it is possible to select individual nematodes for fixation. We were able to HPF complete adults and preserve the morphology in an enhanced fashion compared to chemically fixed tissue. Cellular organelles, especially mitochondria, were much better preserved. Uterine embryos protected by the intact eggshell were excellently preserved without the need for elaborate techniques. Antigenicity with MH27 and ICB4 antisera was tested. With the MH27 serum, an adequate, reproducible, specific binding pattern with chemically fixed tissue could only be achieved using purified antibodies, whereas with highpressure freezing, unpurified MH27 antisera was effective. For ICB4 antisera, a reproducible specific binding pattern was achieved at a concentration of primary antiserum 1000 × lower than that for chemically fixed tissue.