This study was supported by National Research Foundation of South Korea: Mid-career scientist grant (2014002855), and Ministry of Industry, Trade, and Natural Resources: World Premier Material Development Program. This work is also supported by in part by Center for Nature-inspired Technology (CNiT) in KAIST Institute for NanoCentury (KINC).

All animal care and experiments are performed in accordance with the ethical protocol provided by the KAIST (Korea Advanced Institute of Science and Technology) IRB (Institutional Review Board).
1. TAPE Formation
<ol>
	<li>For preparing a TA solution, place a 4 ml-sized glass vial on a magnetic stirrer, and add 1 ml of distilled water with a stirring bar. Add 1 g of tannic acid to the vial, and dissolve it in the water by gentle stirring at 200 rpm for more than 1 hr. When the TA is completely dissolved, the mixture becomes transparent with a brown color.</li>
	<li>Prepare a PEG solution by adding 1 g of PEG powder (4-arms, 10 kDa, and linear, 4.6 kDa) to 1 ml of distilled water followed by mixing them by vortexing for few seconds to make a white slurry. Keep this slurry in the incubator at 60 &#176;C for 10 min. until the white one becomes completely clear. 
	NOTE: The melting point of PEG with 10 kDa molecular weight is around 55 - 60 &#176;C, and the 4 kDa one is 53 - 58 &#176;C. Melted PEG becomes water-miscible so that a high concentration of PEG in water up to 1 g/ml can be achieved as a clear solution. Once a clear PEG solution is formed at a high temperature, the solution is still stable at room temperature after cooling.</li>
	<li>Add 329 &#181;l of the PEG (4-arms, 10 kDa) solution prepared in step 1.2 to 671 &#181;l of the TA solution prepared in step 1.1 (In the case of a linear PEG with 4.6 kDa, add 311 &#181;l of a PEG solution to 689 &#181;l of a TA solution) in a micro-centrifuge tube. Gently blend the two viscous and honey-like solutions with a narrow spatula to mix them homogeneously. 
	CAUTION: Both solutions are quite viscous, so the scientist must slowly but sufficiently pull up and transfer the solutions with a micropipette.</li>
	<li>Spin the mixture prepared in step 1.3 at 12,300 x g for 3 min in a centrifuge equipped with a fixed-angle rotor.</li>
	<li>Carefully remove as much of the supernatant as possible using a micropipette, and collect the product that has settled down: This is the fully formed TAPE. After TAPE formation, store it in the refrigerator (4 - 8&#160;&#176;C) for up to several weeks.&#160;NOTE: TAPE can be sterilized by gamma radiation or electron beam treatment prior to use in surgical applications.</li>
</ol>
2. Measurement of the Adhesion Strength of TAPE&#160;
<ol>
	<li>Prepare two pieces of porcine skin tissue with a diameter of 6 mm by cutting with a biopsy punch after removing all fat on the skin tissue. 
	NOTE: The porcine skin tissue was obtained from healthy porcine flank skin and was purchased from a local meat market located in Daejeon in South Korea.</li>
	<li>Apply commercial cyanoacrylate glue to the outer side of each tissue, and attach the tissue to the metallic rod. 
	NOTE: The metallic rod is used as a supplementary handle so tissues are not directly gripped by the machine. Accordingly, it can be replaced with other materials following the configuration of the tensile machine.</li>
	<li>Apply a drop of TAPE (a drop of TAPE is approximately 3 - 6 mg) to one side of the tissue. Then, spread the TAPE uniformly using another tissue between the two tissues on their inner sides so they are attached as shown in Figure 2A.</li>
	<li>Then, manually attach and detach the two sides of tissues several times to homogenously mix and maximize the interface between each tissue and TAPE.</li>
	<li>With the UTM, carefully grip each side of the rod. The adhesion strength will be determined by the force needed to detach two tissues attached with TAPE. First, apply a force of 20 N for 1 min. Next, with the machine, pull each rod in an opposite direction at a rate of 1 mm/min. until the tissues are completely detached. 
	NOTE: Data will be given as a force-distance (F-D) curve detected by the motion of each rod.</li>
	<li>Calculate the adhesion strength of TAPE by dividing the maximum force (kN) shown at the F-D curve achieved in step 2.5 by the specimen surface area, that is, 3.14 x (0.003 m)2.</li>
	<li>For monitoring the adhesion strength in the presence of water, add 20 &#181;l of water on the detached area between two tissues, and attach them immediately. With the machine, perform the detachment test again.</li>
</ol>
3. In Vitro Degradation Test
<ol>
	<li>Cut a cap (d = 8 mm) of micro-centrifuge tube, and weigh the cap to define it as Wc.</li>
	<li>Fill the cap with 150 mg of TAPE, and weigh all together again to set it as a total initial weight W0. 
	CAUTION: Do not overload TAPE in the cap. The height of TAPE should be lower than the top of the cap, as it can be a physical barrier to a stream of PBS buffer generated by the stirring process during the incubation in step 3.4.</li>
	<li>Put the cap containing TAPE into a cell culture flask (75 cm2), and add 50 ml of PBS buffer (1x, pH 7.4) to the cell culture flask so the TAPE in the cap is completely immersed in the PBS buffer, as shown in Figure 3A (n = 5).</li>
	<li>Incubate the cell culture flask prepared in step 3.3 in an orbital shaking incubator at 37 &#176;C, similar to physiological conditions, with gentle stirring (50 rpm). 
	CAUTION: Keep the stirring condition at 50 rpm. Higher rpm might cause a collapse of TAPE.</li>
	<li>At each time point, take the cap with TAPE from the cell culture flask, and then dry them by blowing nitrogen gas. Weigh the cap containing remaining TAPE. Set the weight at each time point to Wt. Replace the fresh PBS again, and shake it again after measuring Wt at each time point.</li>
	<li>Calculate the relative remaining weight (%) the following equation. 
	Relative remaining weight (%) = (Wt&#160;- Wc)/(W0&#160;- Wc) x 100%</li>
</ol>
4. Hemostatic Ability of TAPE
&#160; &#160; &#160; &#160;NOTE: All animal experiments should be performed in accordance with the guidelines and ethical protocol provided by the Korean Ministry of Health and Welfare.
<ol>
	<li>To evaluate the in vivo hemostatic ability, review the hemorrhaging mouse liver model as described in ref 24.</li>
	<li>Anesthetize fifteen mice (normal ICR mouse, 6 weeks, 30 - 35 g, male) with an intraperitoneal injection of tiletamine-zolazepam (33.333 mg/kg) and xylazine (7.773 mg/kg) (n = 5 per group). To confirm proper anesthetization, pinch the animal&#39;s paw gently and observe movements such as withdrawing the paw, etc. No movement indicates that the animal is sufficiently anesthetized to do surgery.</li>
	<li>To prevent dryness of animal&#39;s eyes, apply vet ointment to eyes sufficiently while under anesthesia. Expose the liver via a midline abdominal incision, and prick the liver with an 18 G needle to induce bleeding.</li>
	<li>Remove the flowing blood with sterile gauze, and put 100 &#181;l of TAPE or fibrin glue (positive control) immediately on the bleeding site. 
	NOTE: No further suturing is needed after applying TAPE due to its highly blood-resistant adhesive properties on wound tissues. For the negative control, no treatment occurs at the site of bleeding.</li>
	<li>In each case, put a filter paper with known mass underneath the liver to collect the blood from the damage site. Replace the paper with a fresh one every 30 sec&#160;for 4 times (i.e., 2 min).</li>
	<li>Measure the mass of absorbed blood on each filter paper collected every 30 sec. After the animal experiment, sacrifice the mice through CO2 asphyxiation euthanasia.</li>
</ol>

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The authors have nothing to disclose.

We developed an entirely new class of hemostatic adhesive named TAPE inspired by the water-resistant molecular interaction of a plant-derived polyphenolic compound, TA. TA is a representative hydrolysable tannin that has significantly attracted attention due to its anti-oxidant, anti-bacterial, anti-mutagenic, and anti-carcinogenic properties.
The process of making TAPE is extremely simple, scalable, and environmentally friendly, as it is just the one-step mixing of two aqueous solutions follo...

In a past decade, efforts have been made to replace current surgical sutures and staples to close wounds with biodegradable/bioabsorbable adhesives due to their convenience in usage and low tissue invasiveness during surgical treatments. Commercially available tissue-adhesives are classified into four types: (1) cyanoacrylate derivatives1, (2) fibrin glues formed by enzymatic conversion from fibrinogen to fibrin polymers by thrombin2,3, (3) protein-based materials such as chemically or physically cross-linked albumin and/or gelatin4,5, and (4) synthetic polymer-based ones6. Although they have been used in many clinical applications, all adhesives have their own intrinsic disadvantages and drawbacks that can be obstacles to their widespread usage. Cyanoacrylate-based glues show high adhesion strength to tissues, but their toxic by-products such as cyanoacetate and formaldehyde formed during degradation, often cause significant degrees of inflammatory responses7. Fibrin glues and albumin or gelatin-based materials have safety issues regarding the transmission of infectious components, such as viruses from animal sources: human blood plasma for fibrin glues and animals including cattle, chicken, pigs, and fish for gelatin-based glues8. Although a few synthetic polymer-based adhesives have been approved by the Federal Drug Administration (FDA), most adhesives made of synthetic polymers continue to have difficulties in minimizing the manufacturing process steps and achieving biocompatibility9. Most importantly, all glues suffer from poor mechanical and adhesion strength to wet tissues10. Recently, biomimetic tissue adhesives inspired by marine mussels11-13, geckos14, gecko with mussel15, and endoparasitic worms16 have been emerging as promising alternatives to current medical glues due to their tunable mechanical and adhesive properties with biocompatibility. However, to this day, there are still issues to be addressed before they become commercial products17.
Here, we report an entirely new type of medical glue called TAPE that is prepared by the intermolecular hydrogen bonding between a plant-derived adhesive molecule, Tannic acid (TA), and a bio-inert polymer Poly(ethylene glycol) (PEG), as its name indicates. TA is a representative hydrolysable tannin ubiquitously found during the secondary metabolism of plants. It has attracted much attention due to its anti-oxidant, anti-mutagenic, and anti-carcinogenic properties and has been shown to participate in supramolecular interactions with many polymers, such as poly(N-isopropylacrylamide) (PNIPAM) and poly(N-vinylpyrrolidone) (PVPON), to form layer-by-layer (LbL) films18-20 and drug-releasing microcapsules21-23. In this study, we discover that TA can act as an efficient water-resistant adhesive functional moiety to form a medical adhesive, TAPE. By simple mixing with TA, a non-fouling polymer PEG becomes a supramolecular glue with 2.5-fold increased adhesion strength compared with commercial fibrin glue, and this adhesion was maintained throughout up to 20 cycles of attachment and detachment, even in the presence of water. Its hemostatic ability was tested on a liver bleeding model in vivo and showed good hemostatic ability to stop bleeding within a few seconds. TAPE has its significant meaning in a related field as the first plant-derived adhesive that can reveal new insight into solving the drawbacks of current problems with bio-inspired approaches. We also expect the widespread use of TAPE in a variety of medical and pharmaceutical applications such as muco-adhesives, drug-releasing patches, wound-care dressings, and others due to its simple preparation method, scalability, tunable biodegradation rate, as well as highly wet-resistant adhesion properties.

<table><tbody><tr><td>Tannic acid</td><td>Sigma-aldrich</td><td>403040</td><td></td></tr><tr><td>Poly(ethylene oxide), 4-arm, hydroxy terminated</td><td>Aldrich</td><td>565709</td><td>Averge Mn ~ 10,000</td></tr><tr><td>Poly(ethylene glycol)</td><td>Aldrich</td><td>373001</td><td>Average Mn 4,600</td></tr><tr><td>Biopsy punch</td><td>Miltex</td><td>33-36</td><td>Diameter = 6 mm</td></tr><tr><td>Aron Alpha</td><td>Toagosei Co., Ltd.</td><td></td><td>Instant glue</td></tr><tr><td>Universal testing machine (UTM)</td><td>Instron</td><td>5583</td><td></td></tr><tr><td>Microcentrifuge tubes</td><td>SPL life science</td><td>60015</td><td>1.5 ml</td></tr><tr><td>Petri dish</td><td>SPL life science</td><td>10090</td><td>90 x 15 mm</td></tr><tr><td>Sodium phosphate monobasic</td><td>Sigma</td><td>S5011</td><td>1x PBS ingredient</td></tr><tr><td>Sodium phosphate dibasic</td><td>Sigma</td><td>S5136</td><td>1x PBS ingredient</td></tr><tr><td>Sodium chloride</td><td>Duchefa biochemie</td><td>S0520.5000</td><td>1x PBS ingredient</td></tr><tr><td>Incubating shaker</td><td>Lab companion</td><td>SIF6000R</td><td></td></tr><tr><td>ICR mice</td><td>Orient bio</td><td>Normal ICR mouse</td><td>6 weeks, 30 - 35 g, male</td></tr><tr><td>Tiletamine-zolazepam (Zoletil 50)</td><td>Virbac</td><td></td><td></td></tr><tr><td>Zylazine (Rompun)</td><td>Bayer</td><td></td><td></td></tr><tr><td>PrecisionGlide&lt;sup&gt;TM&lt;/sup&gt; needle (18 G)</td><td>BD</td><td>302032</td><td>18 G</td></tr><tr><td>Filter paper</td><td>Whatman</td><td>1001 125</td><td>Diameter = 125 mm</td></tr><tr><td>Parafilm</td><td>Bemis Flexible Pakaging</td><td>PM996</td><td></td></tr></tbody></table>

tape: a biodegradable hemostatic glue inspired by a ubiquitous compound in plants for surgical application

This video describes the simplest protocol for preparing biodegradable surgical glue that has an effective hemostatic ability and greater water-resistant adhesion strength than commercial tissue adhesives. Medical adhesives have attracted great attention as potential alternative tools to sutures and staples due to their convenience in usage with minimal invasiveness. Although there are several protocols for developing tissue adhesives including those commercially available such as fibrin glues and cyanoacrylate-based materials, mostly they require a series of chemical syntheses of organic molecules, or complicated protein-purification methods, in the case of bio-driven materials (i.e., fibrin glue). Also, the development of surgical glues exhibiting high adhesive properties while maintaining biodegradability is still a challenge due to difficulties in achieving good performance in the wet environment of the body. We illustrate a new method to prepare a medical glue, known as TAPE, by the weight-based separation of a water-immiscible supramolecular aggregate formed after a physical mixing of a plant-derived, wet-resistant adhesive molecule,&#160;Tannic Acid (TA), and a well-known biopolymer, Poly(Ethylene) glycol (PEG). With our approach, TAPE shows high adhesion strength, which is 2.5-fold more than commercial fibrin glue in the presence of water. Furthermore, TAPE is biodegradable in physiological conditions and can be used as a potent hemostatic glue against tissue bleeding. We expect the widespread use of TAPE in a variety of medical settings and drug delivery applications, such as polymers for muco-adhesion, drug depots, and others.

TAPE is a supramolecular aggregate that settles down after centrifuging the mixture of two aqueous solutions containing TA (1 g/ml in distilled water) and PEG (1 g/ml in distilled water) with 2:1 volume ratio (Figure 1A). The mixing ratio is the key factor in achieving high adhesion strength; when TAPE is formed by a 2:1 mixing ratio, 20 units of the hydroxyl group (-OH) in 25 units of TA interact with each ether group (-O-) in PEG, resulting in the highest intermolecular...

Watch this Scientific Journal Video about TAPE: A Biodegradable Hemostatic Glue Inspired by a Ubiquitous Compound in Plants for Surgical Application at JoVE.com

TAPE: A Biodegradable Hemostatic Glue Inspired by a Ubiquitous Compound in Plants for Surgical Application

We describe the simplest protocol to prepare biodegradable medical glue that has an effective hemostatic ability. TAPE is a water-immiscible supramolecular aggregate prepared by mixing of tannic acid, a ubiquitous compound found in plants, and poly(ethylene) glycol, yielding a 2.5 times greater water-resistant adhesion compared with commercial fibrin glue.

This video describes the simplest protocol for preparing biodegradable surgical glue that has an effective hemostatic ability and greater water-resistant ...

tape-biodegradable-hemostatic-glue-inspired-ubiquitous-compound

Research

JoVE Journal

Bioengineering

14.1K Views.  Korea Advanced Institute of Science and Technology (KAIST). We describe the simplest protocol to prepare biodegradable medical glue that has an effective hemostatic ability. TAPE is a water-immiscible supramolecular aggregate prepared by mixing of tannic acid, a ubiquitous compound found in plants, and poly(ethylene) glycol, yielding a 2.5 times greater water-resistant adhesion compared with commercial fibrin glue.

Video: TAPE: A Biodegradable Hemostatic Glue Inspired by a Ubiquitous Compound in Plants for Surgical Application

Engineering Biological-Based Vascular Grafts Using a Pulsatile Bioreactor

Much effort has been devoted to develop and advance the methodology to regenerate functional small-diameter arterial bypasses. In the physiological environment, both mechanical and chemical stimulation are required to maintain the proper development and functionality of arterial vessels1,2.
Bioreactor culture systems developed by our group are designed to support vessel regeneration within a precisely controlled chemo-mechanical environment mimicking that of native vessels. Our bioreactor assembly and maintenance procedures are fairly simple and highly repeatable3,4. Smooth muscle cells (SMCs) are seeded onto a tubular polyglycolic acid (PGA) mesh that is threaded over compliant silicone tubing and cultured in the bioreactor with or without pulsatile stimulation for up to 12 weeks. There are four main attributes that distinguish our bioreactor from some predecessors. 1) Unlike other culture systems that simulate only the biochemical surrounding of native blood vessels, our bioreactor also creates a physiological pulsatile environment by applying cyclic radial strain to the vessels in culture. 2) Multiple engineered vessels can be cultured simultaneously under different mechanical conditions within a controlled chemical environment. 3) The bioreactor allows a mono layer of endothelial cells (EC) to be easily coated onto the luminal side of engineered vessels for animal implantation models. 4) Our bioreactor can also culture engineered vessels with different diameter size ranged from 1 mm to 3 mm, saving the effort to tailor each individual bioreactor to fit a specific diameter size. 
The engineered vessels cultured in our bioreactor resemble native blood vessels histologically to some degree. Cells in the vessel walls express mature SMC contractile markers such as smooth muscle myosin heavy chain (SMMHC)3. A substantial amount of collagen is deposited within the extracellular matrix, which is responsible for ultimate mechanical strength of the engineered vessels5. Biochemical analysis also indicates that collagen content of engineered vessels is comparable to that of native arteries6. Importantly, the pulsatile bioreactor has consistently regenerated vessels that exhibit mechanical properties that permit successful implantation experiments in animal models3,7. Additionally, this bioreactor can be further modified to allow real-time assessment and tracking of collagen remodeling over time, non-invasively, using a non-linear optical microscopy (NLOM)8. To conclude, this bioreactor should serve as an excellent platform to study the fundamental mechanisms that regulate the regeneration of functional small-diameter vascular grafts.

Our group has developed a bioreactor culture system that mimics the physiological pulsatile stresses of the cardiovascular system to regenerate implantable small-diameter vascular grafts.

Much effort has been devoted to develop and advance the methodology to regenerate functional small-diameter arterial bypasses. In the physiological ...

A Chitosan Based, Laser Activated Thin Film Surgical Adhesive, 'SurgiLux': Preparation and Demonstration

Sutures are a 4,000 year old technology that remain the 'gold-standard' for wound closure by virtue of their repair strength (~100 KPa). However, sutures can act as a nidus for infection and in many procedures are unable to effect wound repair or interfere with functional tissue regeneration.1 Surgical glues and adhesives, such as those based on fibrin and cyanoacrylates, have been developed as alternatives to sutures for the repair of such wounds. However, current commercial adhesives also have significant disadvantages, ranging from viral and prion transfer and a lack of repair strength as with the fibrin glues, to tissue toxicity and a lack of biocompatibility for the cyanoacrylate based adhesives. Furthermore, currently available surgical adhesives tend to be gel-based and can have extended curing times which limit their application.2 Similarly, the use of UV lasers to facilitate cross-linking mechanisms in protein-based or albumin 'solders' can lead to DNA damage while laser tissue welding (LTW) predisposes thermal damage to tissues.3 Despite their disadvantages, adhesives and LTW have captured approximately 30% of the wound closure market reported to be in excess of US $5 billion per annum, a significant testament to the need for sutureless technology.4
In the pursuit of sutureless technology we have utilized chitosan as a biomaterial for the development of a flexible, thin film, laser-activated surgical adhesive termed 'SurgiLux'. This novel bioadhesive uses a unique combination of biomaterials and photonics that are FDA approved and successfully used in a variety of biomedical applications and products. SurgiLux overcomes all the disadvantages associated with sutures and current surgical adhesives (see Table 1).
In this presentation we report the relatively simple protocol for the fabrication of SurgiLux and demonstrate its laser activation and tissue weld strength. SurgiLux films adhere to collagenous tissue without chemical modification such as cross-linking and through irradiation using a comparatively low-powered (120 mW) infrared laser instead of UV light. Chitosan films have a natural but weak adhesive attraction to collagen (~3 KPa), laser activation of the chitosan based SurgiLux films emphasizes the strength of this adhesion through polymer chain interactions as a consequence of transient thermal expansion.5 Without this 'activation' process, SurgiLux films are readily removed.6-9 SurgiLux has been tested both in vitro and in vivo on a variety of tissues including nerve, intestine, dura mater and cornea. In all cases it demonstrated good biocompatibility and negligible thermal damage as a consequence of irradiation.6-10

The fabrication of a novel, flexible thin film surgical adhesive from FDA approved ingredients, chitosan and indocyanine green is described. Bonding of this adhesive to collagenous tissue through a simple activation process with a low-powered infra-red laser is demonstrated.

Sutures are a 4,000 year old technology that remain the 'gold-standard' for wound closure by virtue of their repair strength (~100 KPa). However, sutures ...

Engineering a Bilayered Hydrogel to Control ASC Differentiation

Natural polymers over the years have gained more importance because of their host biocompatibility and ability to interact with cells in vitro and in vivo. An area of research that holds promise in regenerative medicine is the combinatorial use of novel biomaterials and stem cells. A fundamental strategy in the field of tissue engineering is the use of three-dimensional scaffold (e.g., decellularized extracellular matrix, hydrogels, micro/nano particles) for directing cell function. This technology has evolved from the discovery that cells need a substrate upon which they can adhere, proliferate, and express their differentiated cellular phenotype and function 2-3. More recently, it has also been determined that cells not only use these substrates for adherence, but also interact and take cues from the matrix substrate (e.g., extracellular matrix, ECM)4. Therefore, the cells and scaffolds have a reciprocal connection that serves to control tissue development, organization, and ultimate function. Adipose-derived stem cells (ASCs) are mesenchymal, non-hematopoetic stem cells present in adipose tissue that can exhibit multi-lineage differentiation and serve as a readily available source of cells (i.e. pre-vascular endothelia and pericytes). Our hypothesis is that adipose-derived stem cells can be directed toward differing phenotypes simultaneously by simply co-culturing them in bilayered matrices1. Our laboratory is focused on dermal wound healing. To this end, we created a single composite matrix from the natural biomaterials, fibrin, collagen, and chitosan that can mimic the characteristics and functions of a dermal-specific wound healing ECM environment.

This protocol focuses on utilizing the inherent ability of stem cells to take cue from their surrounding extracellular matrix and be induced to differentiate into multiple phenotypes. This methods manuscript extends our description and characterization of a model utilizing a bilayered hydrogel, composed of PEG-fibrin and collagen, to simultaneously co-differentiate adipose-derived stem cells1.

Natural polymers over the years have gained more importance because of their host biocompatibility and ability to interact with cells in vitro and in ...

Fabrication and Application of Rose Bengal-chitosan Films in Laser Tissue Repair

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two tissue edges1,2. These are then irradiated by a laser that is selectively absorbed by the RB. The resulting photochemical reactions supposedly crosslink the collagen fibers in the tissue with minimal heat production3. In this report, RB has been incorporated in thin chitosan films to fabricate a novel tissue adhesive that is laser-activated. Adhesive films, based on chitosan and containing ~0.1 wt% RB, are fabricated and bonded to calf intestine and rat tibial nerves by a solid state laser (&lambda;=532 nm, Fluence~110 J/cm2, spot size~0.5 cm). A single-column tensiometer, interfaced with a personal computer, is used to test the bonding strength. The RB-chitosan adhesive bonds firmly to the intestine with a strength of 15 &plusmn; 6 kPa, (n=30). The adhesion strength drops to 2 &plusmn; 2 kPa (n=30) when the laser is not applied to the adhesive. The anastomosis of tibial nerves can be also completed without the use of sutures. A novel chitosan adhesive has been fabricated that bonds photochemically to tissue and does not require sutures.

Sutures are usually needed to repair tissue during surgical procedures. However, their application can be problematic as they are invasive and may damage tissue. The fabrication and application methods of a novel tissue adhesive are here reported. This adhesive film is laser-activated and does not require the use of sutures.

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two ...

Pluripotent Stem Cell Derived Cardiac Cells for Myocardial Repair

Human induced pluripotent stem cells (hiPSCs) must be fully differentiated into specific cell types before administration, but conventional protocols for differentiating hiPSCs into cardiomyocytes (hiPSC-CMs), endothelial cells (hiPSC-ECs), and smooth muscle cells (SMCs) are often limited by low yield, purity, and/or poor phenotypic stability. Here, we present novel protocols for generating hiPSC-CMs, -ECs, and -SMCs that are substantially more efficient than conventional methods, as well as a method for combining cell injection with a cytokine-containing patch created over the site of administration. The patch improves both the retention of the injected cells, by sealing the needle track to prevent the cells from being squeezed out of the myocardium, and cell survival, by releasing insulin-like growth factor (IGF) over an extended period. In a swine model of myocardial ischemia-reperfusion injury, the rate of engraftment was more than two-fold greater when the cells were administered with the cytokine-containing patch comparing to the cells without patch, and treatment with both the cells and the patch, but not with the cells alone, was associated with significant improvements in cardiac function and infarct size.

We present three novel and more efficient protocols for differentiating human induced pluripotent stem cells into cardiomyocytes, endothelial cells, and smooth muscle cells and a delivery method that improves the engraftment of transplanted cells by combining cell injection with patch-mediated cytokine delivery.

Human induced pluripotent stem cells (hiPSCs) must be fully differentiated into specific cell types before administration, but conventional protocols for ...

Developmental Biology

Characterization of Leukocyte-platelet Rich Fibrin, A Novel Biomaterial

Autologous platelet concentrates represent promising innovative tools in the field of regenerative medicine and have been extensively used in oral surgery. Unlike platelet rich plasma (PRP) that is a gel or a suspension, Leukocyte-Platelet Rich Fibrin (L-PRF) is a solid 3D fibrin membrane generated chair-side from whole blood containing no anti-coagulant. The membrane has a dense three dimensional fibrin matrix with enriched platelets and abundant growth factors. L-PRF is a popular adjunct in surgeries because of its superior handling characteristics as well as its suturability to the wound bed. The goal of the study is to demonstrate generation as well as provide detailed characterization of relevant properties of L-PRF that underlie its clinical success.

Leucocyte-Platelet Rich Fibrin (L-PRF) represents an FDA cleared preparation of autologous platelet concentrates that possesses unique fibrin architecture, enriched platelets and abundant growth factors. Here, we present a protocol for chair-side generation of L-PRF as well as evaluate its mechanical properties including uniaxial testing and suture retention strength testing.

Autologous platelet concentrates represent promising innovative tools in the field of regenerative medicine and have been extensively used in oral ...

Polyelectrolyte Complex for Heparin Binding Domain Osteogenic Growth Factor Delivery

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone fusion. Large doses of highly potent biological agents are required due to growth factor instability as a result of rapid enzymatic degradation as well as carrier inefficiencies in localizing sufficient amounts of growth factor at implant sites. Hence, strategies that prolong the stability of growth factors such as BMP-2/NELL-1, and control their release could actually lower their efficacious dose and thus reduce the need for larger doses during future bone regeneration surgeries. This in turn will reduce side effects and growth factor costs. Self-assembled PECs have been fabricated to provide better control of BMP-2/NELL-1 delivery via heparin binding and further potentiate growth factor bioactivity by enhancing in vivo stability. Here we illustrate the simplicity of PEC fabrication which aids in the delivery of a variety of growth factors during reconstructive bone surgeries.

Self-assembled polyelectrolyte complexes (PEC) fabricated from heparin and protamine were deposited on alginate beads to entrap and regulate the release of osteogenic growth factors. This delivery strategy enables a 20-fold reduction of BMP-2 dose in spinal fusion applications. This article illustrates the benefits and fabrication of PECs.

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone ...

A Hydrogel Construct and Fibrin-based Glue Approach to Deliver Therapeutics in a Murine Myocardial Infarction Model.

The murine MI model is widely recognized in the field of cardiovascular disease, and has consistently been used as a first step to test the efficacy of treatments in vivo1. The traditional, established protocol has been further fine-tuned to minimize the damage to the animal. Notably, the pectoral muscle layers are teased away rather than simply cut, and the thoracotomy is approached intercostally as opposed to breaking the ribs in a sternotomy, preserving the integrity of the ribcage. With these changes, the overall stress on the animal is decreased. 
Stem cell therapies aimed to alleviate the damage caused by MIs have shown promise over the years for their pro-angiogenic and anti-apoptotic benefits. Current approaches of delivering cells to the heart surface typically involve the injection of the cells either near the damaged site, within a coronary artery, or into the peripheral blood stream2-4. While the cells have proven to home to the damaged myocardium, functionality is limited by their poor engraftment at the site of injury, resulting in diffusion into the blood stream5. This manuscript highlights a procedure that overcomes this obstacle with the use of a cell-encapsulated hydrogel patch. The patch is fabricated prior to the surgical procedure and is placed on the injured myocardium immediately following the occlusion of the left coronary artery. To adhere the patch in place, biocompatible external fibrin glue is placed directly on top of the patch, allowing for it to dry to both the patch and the heart surface. This approach provides a novel adhesion method for the application of a delicate cell-encapsulating therapeutic construct.

This protocol aims to alleviate the limitation of poor cell engraftment for stem cell treatment of myocardial infarctions through the use of a hydrogel system and a fibrin-based glue. With this approach, cell-to-tissue contact post-infarction can be maintained, increasing the therapeutic potential of beneficial agents at the site of injury.

The murine MI model is widely recognized in the field of cardiovascular disease, and has consistently been used as a first step to test the efficacy of ...

Medicine

Synthesis of Strong Adhesive Hydrogel, Gelatin O-Nitrosobenzaldehyde

Adhesive materials have become popular biomaterials in the field of biomedical and tissue engineering. In our previous work, we presented a new material - gelatin o-nitrosobenzaldehyde (gelatin-NB) - which is mainly used for tissue regeneration and has been validated in animal models of corneal injury and inflammatory bowel disease. This is a novel hydrogel formed by modifying biological gelatin with o-nitrosobenzaldehyde (NB). Gelatin-NB was synthesized by activating the carboxyl group of NB-COOH and reacting with gelatin through 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The obtained compound was purified to generate the final product, which can be stably stored for at least 18 months. NB has a strong adhesion to -NH2 on the tissue, which can form many C = N bonds, thus increasing the adhesion of gelatin-NB to the tissue interface. The preparation process comprises steps for the synthesis of the NB-COOH group, modification of the group, synthesis of gelatin-NB, and purification of the compound. The goal is to describe the specific synthesis process of gelatin-NB in detail and to demonstrate the application of gelatin-NB to damage repair. Moreover, the protocol is presented to further strengthen and expand the nature of the material produced by the scientific community for more applicable scenarios.

The protocol presented here shows the synthesis of a strong adhesive hydrogel gelatin o-nitrosobenzaldehyde (gelatin-NB). Gelatin-NB has rapid and efficient tissue adhesion ability, which can form a strong physical barrier to protect wound surfaces, so it is expected to be applied to the field of injury repair biotechnology.

Adhesive materials have become popular biomaterials in the field of biomedical and tissue engineering. In our previous work, we presented a new material - ...

Occlusion of the Great and Small Saphenous Vein Using Copolymeric Glue Based on N-Butyl Cyanoacrylate and Methacryloxy Sulfolane

We present the preliminary results of a longitudinal observational study aimed at evaluating the effectiveness and safety at different short- and long-term follow-ups of vascular occlusion of the great saphenous vein (GSV) and small saphenous vein (SSV) affected by severe pathological reflux, using an innovative modified cyanoacrylate surgical glue composed of N-butyl cyanoacrylate and methacryloxy sulfolane (NBCA+MS). Ninety patients, prospectively recruited for 1 year, underwent the study with EcoColor-Doppler (ECD) to evaluate the maximum diameters of the GSV and SSV in the orthostatic position and the reflux time (RT). An RT greater than 0.5 s was considered pathologic. Clinical, etiology, anatomy, and pathophysiology (CEAP) assessment was used for the complete evaluation of each patient in the study. All the patients were treated by NBCA+MS glue to obtain vein occlusion and observed before treatment (baseline; T0), within 6 h after treatment (T1), 1 month after treatment (T2), 3 months after treatment (T3), 6 months after treatment (T4), and 1 year after treatment (T5). Chi-square (&#967;) analysis was performed to evaluate the effectiveness and safety of the treatment. All the patients participated in the entire duration of the study. Complete occlusion was maintained in 100% of patients at T1, 98.9% at T2 and T3, and 97.8% at T4 and T5 (p &lt; 0.001). None of the patients suffered from post-surgical thrombosis. No blue hyperpigmentation, or paresthesia was observed during the entire observation period. Immediately after treatment, 7.7% of patients needed painkillers; 1 week after treatment, 100% of patients returned to normal life. Vascular occlusion of the great or small saphenous vein using NBCA+MS glue is a safe procedure with persistent benefits after a 1 year follow-up. This procedure can be performed with local anesthesia, allowing a quick return to normal life. Thanks to its low invasiveness, the treatment is not painful.

Here, we present a protocol to treat the great saphenous vein (GSV) and the small saphenous vein (SSV) affected by severe pathological reflux, using an original sclerosing and embolizing cyanoacrylate-based glue composed of N-butyl cyanoacrylate and methacryloxy sulfolane (NBCA+MS).