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Purpose: A control algorithm for radio-frequency-induced intestinal tissue fusion was developed to explore the effects of different control parameters on intestinal tissue fusion. Materials and methods: Radio-frequency-induced fusion was performed on ex vivo small intestine tissue. The effect on the fusion was observed by changing the control parameters (power, interval time, and terminal impedance) in the algorithm. The quality of fusion was evaluated using the burst pressure and thermal damage measurement. Histological evaluation was used to assess the fusion quality indirectly. Results: A maximum burst pressure of 8.460 ± 0.2674 KPa was acquired when the power was set to 100 W, the interval time was set to 2000 ms, and the terminal impedance was set to 50 Ω. Moreover, the thermal damage range increased with an increase in power but decreased with an increase in the interval time and terminal impedance. Furthermore, the thermal damage range and temperature were presumably related. Conclusions: For an ex vivo small intestine tissue, the appropriate control parameters could be set when the power was approximately 100 W, the interval time was approximately 2000 ms, and the terminal impedance was approximately 50 Ω. This study could provide a basis for the selection of control parameters for intestinal tissue fusion.

Background Recent advances in tissue engineering have led to the development of the concept of bioprinting as an interesting alternative to traditional tissue engineering approaches. Biopaper, a biomimetic hydrogel, is an essential component of the bioprinting process. Objective The aim of this work was to synthesize a biopaper made of fibrin-gelatin hybrid hydrogel for application in skin bioprinting. Methods Different composition percentages of the two biopolymer hydrogels, fibrin-gelatin, have been studied for the construction of the biopaper and were examined in terms of water absorption, biodegradability, glucose absorption, mechanical properties and water vapor transmission. Subsequently, tissue fusion study was performed on prepared 3T3 fibroblast cell line pellets embedded into the hydrogel. Results Based on the obtained results, fibrin-gelatin blend hydrogel with the same proportion of two components provides a natural scaffold for fibroblast-based bioink embedding and culture. Conclusions The suggested optimized hydrogel was a suitable candidate as a biopaper for skin bioprinting technology.

As minimally invasive surgical techniques progress, the demand for efficient, reliable methods for vascular ligation and tissue closure becomes pronounced. The surgical advantages of energy-based vessel sealing exceed those of traditional, compression-based ligatures in procedures sensitive to duration, foreign bodies, and recovery time alike. Although the use of energy-based devices to seal or transect vasculature and connective tissue bundles is widespread, the breadth of heating strategies and energy dosimetry used across devices underscores an uncertainty as to the molecular nature of the sealing mechanism and induced tissue effect. Furthermore, energy-based techniques exhibit promise for the closure and functional repair of soft and connective tissues in the nervous, enteral, and dermal tissue domains. A constitutive theory of molecular bonding forces that arise in response to supraphysiological temperatures is required in order to optimize and progress the use of energy-based tissue fusion. While rapid tissue bonding has been suggested to arise from dehydration, dipole interactions, molecular cross-links, or the coagulation of cellular proteins, long-term functional tissue repair across fusion boundaries requires that the reaction to thermal damage be tailored to catalyze the onset of biological healing and remodeling. In this review, we compile and contrast findings from published thermal fusion research in an effort to encourage a molecular approach to characterization of the prevalent and promising energy-based tissue bond.

Heat-induced tissue fusion via radio-frequency (RF) energy has gained wide acceptance clinically and here we present the first optical-Raman-spectroscopy study on tissue fusion samples in vitro. This study provides direct insights into tissue constituent and structural changes on the molecular level, exposing spectroscopic evidence for the loss of distinct collagen fibre rich tissue layers as well as the denaturing and restructuring of collagen crosslinks post RF fusion. These findings open the door for more advanced optical feedback-control methods and characterization during heat-induced tissue fusion, which will lead to new clinical applications of this promising technology. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Large vessels can be reliably sealed with radio frequency current. High apposition pressures are necessary to ensure a high probability of a successful seal. However, the complex architecture of the vessels, particularly arteries, means that results can vary substantially even with similar thermal histories. The relative volume fractions and spatial distributions of collagen, elastin, and smooth muscle dominate the vessel function in vivo and can even vary from proximal to distal locations in the same vessel. We begin by reviewing the architectural features characteristic of porcine and canine large vessels and conclude with an experimental and numerical modeling demonstration of the reasons why cylindrical electrodes are a sub-optimal choice.

Cellular spheroids were studied to determine their use as “bioinks” in the biofabrication of tissue engineered constructs. Specifically, magnetic forces were used to mediate the cyclic longitudinal stretching of tissues composed of Janus magnetic cellular spheroids (JMCSs), as part of a post-processing method for enhancing the deposition and mechanical properties of an extracellular matrix (ECM). The purpose was to accelerate the conventional tissue maturation process via novel post-processing techniques that accelerate the functional, structural, and mechanical mimicking of native tissues. The results of a forty-day study of JMCSs indicated an expression of collagen I, collagen IV, elastin, and fibronectin, which are important vascular ECM proteins. Most notably, the subsequent exposure of fused tissue sheets composed of JMCSs to magnetic forces did not hinder the production of these key proteins. Quantitative results demonstrate that cyclic longitudinal stretching of the tissue sheets mediated by these magnetic forces increased the Young’s modulus and induced collagen fiber alignment over a seven day period, when compared to statically conditioned controls. Specifically, the elastin and collagen content of these dynamically-conditioned sheets were 35- and three-fold greater, respectively, at seven days compared to the statically-conditioned controls at three days. These findings indicate the potential of using magnetic forces in tissue maturation, specifically through the cyclic longitudinal stretching of tissues.

Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (

Fusion of biological tissues through direct and indirect heating is a growing area of medical research, yet there are still major gaps in understanding this procedure. Several companies have developed devices which fuse blood vessels, but little is known about the tissue's response to the stimuli. The need for accurate measurements of tissue behavior during tissue fusion is essential for the continued development and improvement of energy delivery devices. An experimental study was performed to measure the temperatures experienced during tissue fusion and the resulting burst pressure of the fused arteries. An array of thermocouples was placed in the lumen of a porcine splenic artery segment and sealed using a ConMed Altrus thermal fusion device. The temperatures within the tissue, in the device, and at the tissue-device interface were recorded. These measurements were then analyzed to calculate the temperature profile in the lumen of the artery. The temperature in the artery at the site of tissue fusion was measured to range from 142 to 163 °C using the ConMed Altrus. The corresponding burst pressure for arteries fused at this temperature was measured as 416 ± 79 mmHg. This study represents the first known experimental measurement of temperature at the site of vessel sealing found in the literature.

Organ printing utilizes tissue spheroids or filaments as building blocks to fabricate three-dimensional (3D) functional tissues and organs based on a layer-by-layer manufacturing mechanism. These fabricated tissues and organs are envisioned as alternatives to replace the damaged human tissues and organs, which is emerging as a promising solution to solve the organ donor shortage problem being faced all over the world. Inkjetting, one of the key technologies in organ printing, has been widely developed because of its moderate fabrication cost, good process controllability, and scale-up potentials. There are several key steps towards inkjet-based organ printing: generation of droplets from bioink, fabrication of 3D cellular structures, and post-printing tissue fusion and maturation. The droplet formation process is the first step, affecting the overall feasibility of the envisioned organ printing technology. This paper focuses on the ligament flow of the droplet formation process during inkjet printing of b...

Organ printing is a variant of the biomedical application of additive manufacturing (rapid prototyping) technology or layer-by-layer additive biofabrication of 3D tissue and organ constructs using self-assembled tissue spheroids as building blocks. Bioengineering of perfusable intraorgan branched vascular trees incorporated into 3D tissue constructs is essential for the survival of bioprinted thick 3D tissues and organs. In order to design the optimal ‘blueprint’ for digital bioprinting of intraorgan branched vascular trees, the coefficients of tissue retraction associated with post-printing vascular tissue spheroid fusion and remodeling must be determined and incorporated into the original CAD. Using living tissue spheroids assembled into ring-like and tube-like vascular tissue constructs, the coefficient of tissue retraction has been experimentally evaluated. It has been shown that the internal diameter of ring-like and the height of tubular-like tissue constructs are significantly reduced during tissue spheroid fusion. During the tissue fusion process, the individual tissue spheroids also change their shape from ball-like to a conus-like form. A simple formula for the calculation of the necessary number of tissue spheroids for biofabrication of ring-like structures of desirable diameter has been deduced. These data provide sufficient information to design optimal CAD for bioprinted branched vascular trees of different human organs desirable final geometry and size.

Tissue fusion is a method of joining tissue using heat and pressure. Several surgical tool companies have developed devices which perform tissue fusion on blood vessels in order to perform ligation of the vessel [1]. The success or failure of these devices is contingent upon the strength of the bond it creates between opposing sides of the blood vessel lumen, yet little characterization has been done to measure the strength of this interface. Previous studies have examined the strength of tissue fusion using clinically relevant metrics such as burst pressure or tearing strength, but none have explored metrics more appropriate for determining the mechanics of the actual bond, such as peel strength or shear strength [2–3]. These clinical metrics are susceptible to large variations due to tissue composition and geometry. The goal of this study is to measure the bond’s modulus and strength using standard engineering methods. The motivation of the present work is to develop a method for quantitatively measuring the strength of the bond made during tissue fusion. This method can then be applied to quantify the strength of the fusion interface between arterial tissue using other devices and aid in future evaluation and development of tissue fusion devices to maximize the bond strength.Copyright © 2012 by ASME

LigaSure™ is basically a bipolar electric cautery. The LigaSure™ system is made up of an energy platform and handpiece. LigaSure™ tissue fusion, like LigaSure™ vessel sealing, uses the body’s own collagen and elastin to create a permanent fusion zone. When used in liver transection, LigaSure™ can seal and cut vessels faster than manual ligation and is more consistent and reliable than conventional electric cautery. LigaSure™ has the best synergy with the clamp-crush (CC) technique. Use of a LigaSure™ system plus CC technique during liver resection allowed rapid and safe division of the liver parenchyma. The LigaSure™ system, including the equipment such as the handpiece and energy platform, has been improved, and we can transect liver parenchyma more easily and quickly with the new system.

Irreversible thermal alterations in tissue function and structure are used in clinical applications to achieve diverse goals, from lower-temperature tumor ablation to higher-temperature tissue fusion and surgical cutting. The typical formulation in tumor hyperthermia studies, the thermal iso-effect dose, derives from cell-survival studies but describes a single process only over a limited range of temperatures and is thus not suitable for multiple higher-temperature events. Many other thermal damage processes have been described using the Arrhenius kinetic rate of formation approach, which has the advantage that it is inherently quantitative in nature and can easily be compared with quantitative markers of injury or histologic section. The vast majority of Arrhenius studies have been directed toward measurable cellular effects at relatively low temperatures. Some emphasis in this paper has been placed on what is known of higher-temperature processes to support the theme of this issue. This review compares and contrasts the two thermal-damage formulations and reviews methods to convert between them.

A significant challenge of tissue engineering is to build tissues whose size is not limited by diffusion. We are investigating the use of scaffold-free lumen containing toroid-shaped microtissues as minimal building units. Monodispersed H35 cells, a rat hepatocyte cell line, were seeded onto micromolded agarose, forming self-assembled multicellular toroids within 48 h. Toroid and lumen diameter were easily controlled by micromold design, and toroid thickness was controlled by seeding density. When harvested, toroids were stable, but underwent predictable changes over time with their lumens narrowing. When brought into contact, these building units fused in the x-y plane, forming a double-lumen structure, as well as the z plane, forming a tubular structure, which completed within 72 h. Large, multi-luminal structures were assembled by multidimensional fusion of many toroids. Toroid settling was not entirely random, with most toroids lying flat with their lumens oriented along the z axis. The rapid production of toroid building units of controlled dimension and lumen size that undergo predictable changes and that can be fused to form larger structures is a step closer to tissue engineering large porous three-dimensional tissues with high cell density.

Bioengineering of living heart valve substitute suitable for implantation into pediatric patients with heart valve diseases is an unsolved challenge in cardiovascular tissue engineering. In order to identify desirable material properties of such construct, the biomechanical, histological, histochemical and biochemical properties of fetal, perinatal and adult porcine heart valve leaflets have been systematically investigated. It have been shown that increasing in heart valve stiffness during ontogenesis correlates with accumulation of collagen type 1 and increasing level of collagen cross-linking. Tissue spheroids biofabricated from human fat tissue derived stem cells have been employed to engineer leaflet-like construct on compliant electrospun scaffold using self-assembly or tissue fusion approach. Incubation of tissue engineered heart valve leaflet construct with TGFs as well as periostin transfection significantly increased stiffness of tissue engineered heart valve leaflet. These data demonstrated that the heart valve can be biofabricated by tissue fusion or self-assembly of closely placed tissue spheroids and that chemically and genetically induced accelerated tissue maturation and collagen deposition can enhance mechanical properties of tissue engineered leaflet. Further optimization of accelerated tissue maturation technologies could eventually lead to development of living autologous human heart valve tissue engineered construct with natural- like biomechanical properties suitable for pediatric cardiac patients.

Organ printing can be defined as layer-by-layer additive robotic biofabrication of three-dimensional functional living macrotissues and organ constructs using tissue spheroids as building blocks. The microtissues and tissue spheroids are living materials with certain measurable, evolving and potentially controllable composition, material and biological properties. Closely placed tissue spheroids undergo tissue fusion - a process that represents a fundamental biological and biophysical principle of developmental biology-inspired directed tissue self-assembly. It is possible to engineer small segments of an intraorgan branched vascular tree by using solid and lumenized vascular tissue spheroids. Organ printing could dramatically enhance and transform the field of tissue engineering by enabling large-scale industrial robotic biofabrication of living human organ constructs with "built-in" perfusable intraorgan branched vascular tree. Thus, organ printing is a new emerging enabling technology paradigm which represents a developmental biology-inspired alternative to classic biodegradable solid scaffold-based approaches in tissue engineering.

The results of a closed loop thermal feedback controlled laser-assisted tissue welding study in vivo are reported. A series of experiments was carried out to study and compare the weld strength and healing response of sutured and laser welded rat enterotomies with and without temperature feedback control (TFC) using a cryogenically cooled Ho:YAG laser. Although assignment of animals to three groups (control sutured, laser welded with and without TFC) and four observation periods (1, 3, 7, and 21 days) was randomized, several laser welded enterotomies without TFC had complications resulting in death of the animals. Those experiments were repeated. From the failure rates encountered, it is shown that TFC improves the quality of laser-assisted enterotomy closures.

The argon laser has proven to be a valuable tool for the thermodynamic debridement of the periodontal lesion, incisions and tissue fusion. Illustrations of clinical applications and discussion of laser parameters will be provided.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Tissue fusion by laser energy is an intriguing arxi very promising new application for laser technology. In coniparison to using high laser energy to ablate tissue as in the aricplasty application, laser tissue fusion is possible in any soft tissue by deliverir appropriate lc levels of energy to the cppose tissue surfaces. This technology is particularly appealing for vascular applications in inakir sutureless blood vessel anastornosis and for securir the endpOints of erxarterect:amies ani dissection planes. Although there have been limitel evaluations of this technology the preliminary experimental ar1 clinical data is very promisir for continu development arid application.

Two mechanisms of laser tissue fusion, thermal and photochemical, are currently being proposed in several types of tissue. In this study we examined the thermal and histologic components of laser fusion in blood vessels and bowel. CO2 and Argon lasers were used to fuse 1 cm canine arteriotomies and 1 cm rabbit enterotomies. Thermal images were concurrently recorded with an AGA Thermovision camera and computer analyzed. Tissue samples from each weld were subsequently prepared for histologic examination.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Precise tissue apposition and edge eversion are essential for tissue fusion with the CO2 laser. A microtenaculum has been designed to accomplish this without the placement of horizontal mattress stay sutures. This instrument permits tissue orientation and approximation for primary laser fusion as well as for the repair of small gaps present after initial welding.

Tissue fusion using a computerized 1.3 micron YAG laser has been in use in human clinical trails under a FDA investigational device exemption since June, 1988. Animals studies using the 1.3 micron wavelength will be reviewed.