Prevention of retrosternal adhesion by novel biocompatible glue derived from food additives

Controlled release of vancomycin from PEGylated fibrinogen polyethylene glycol diacrylate hydrogel

Surgical site infection (SSI) is a common issue post-surgery which often prolongs hospitalization and can lead to serious complications such as sternal wound infection following cardiac surgery via median sternotomy. Controlled release of suitable antibiotics could allow maximizing drug efficacy and safety, and therefore achieving a desired therapeutic response. In this study, we have developed a vancomycin laden PEGylated fibrinogen-polyethylene glycol diacrylate (PF-PEGDA) hydrogel system that can release vancomycin at a controlled and predictable rate to be applied in SSI prevention. Two configurations were developed to study effect of the hydrogel on drug release, namely, vancomycin laden hydrogel and vancomycin solution on top of blank hydrogel. The relationship between the rigidity of the hydrogel and drug diffusion was found to comply with a universal power law, i.e., softer hydrogels result in a greater diffusion coefficient hence faster release rate. Besides, vancomycin laden hydrogels exhibited burst release, whereas the vancomycin solution on top of blank hydrogels exhibited lag release. A mathematical model was developed to simulate vancomycin permeation through the hydrogels. The permeation of vancomycin can be predicted accurately by using the mathematical model, which provided a useful tool to customize drug loading, hydrogel thickness and stiffness for personalized medication to manage SSI. To evaluate the potential of hydrogels for bone healing applications in cardiovascular medicine, we performed a proof-of-concept median sternotomy in rabbits and applied the hydrogels. The hydrogel formulations accelerated the onset of osteo-genetic processes in rabbits, demonstrating its potential to be used in human.

Hotmelt tissue adhesive with supramolecularly-controlled sol-gel transition for preventing postoperative abdominal adhesion

Postoperative adhesion is a serious and frequent complication, but there is currently no reliable anti-adhesive barrier available due to low tissue adhesiveness, undesirable chemical reactions, and poor operability. To overcome these problems, we report a single-syringe hotmelt tissue adhesive that dissolves upon warming over 40 °C and coheres at 37 °C as a postoperative barrier. Tendon-derived gelatin was conjugated with the ureidopyrimidinone unit to supramolecularly control the sol-gel transition behavior. This functionalization improved bulk mechanical strength, tissue-adhesive properties, and stability under physiological conditions through the augmentation of intermolecular hydrogen bonding by ureidopyrimidinone unit. This biocompatible adhesive prevented postoperative adhesion between cecum and abdominal wall in adhesion models of rats. This hotmelt tissue adhesive has enormous potential to prevent postoperative complications and may contribute to minimally invasive surgery. STATEMENT OF SIGNIFICANCE: There is a strong need to develop medical tissue adhesives with high biocompatibility, tissue adhesiveness, and operatability to prevent postoperative complications. In this report, single syringe, hotmelt-type tissue adhesive was developed by controlling sol-gel transition behavior of gelatin through supramolecular approach. The functionalization of gelatin with quadruple hydrogen bonding improved key features necessary for anti-adhesive barrier including bulk mechanical strength, tissue adhesive property, stability under physiological conditions, and anti-adhesive property. The hotmelt tissue adhesive can be used for a sealant, hemostatic reagent, and wound dressing to prevent postoperative complications including delayed bleeding, perforation, and inflammation and contribute to minimally invasive surgery.

Elucidating the degradation mechanism of a self-degradable dextran-based medical adhesive

We developed a self-degradable medical adhesive, LYDEX, consisting of periodate-oxidized aldehyde-functionalized dextran (AD) and succinic anhydride-treated ε-poly-l-lysine (SAPL). After gelation and adhesion of LYDEX by Schiff base bond formation between the AD aldehyde groups and SAPL amino groups, molecular degradation associated with the Maillard reaction is initiated, but the detailed degradation mechanism remains unknown. Herein, we elucidated the degradation mechanism of LYDEX by analyzing the main degradation products under typical solution conditions in vitro. The degradation of the LYDEX gel with a sodium periodate/dextran content of 2.5/20 was observed using gel permeation chromatography and infrared and ¹H NMR spectroscopy. The AD ratio in the AD-SAPL mixture increased as the molecular weight decreased with the degradation time. This discovery of LYDEX self-degradability is useful for clarifying other polysaccharide hydrogel degradation mechanisms, and valuable for the use of LYDEX in medical applications, such as hemostatic or sealant materials.

Evaluations for surrounding tissue incorporation after implantation of synthetic vascular prostheses in animal models

Incorporation of surrounding tissues after implantation of synthetic vascular prostheses potentially varies in accordance with implanted prostheses. To evaluate post-implant tissue incorporation, we examined surgical, histological and ultrastructural findings after implantation in animal models. Three types of commercially available prostheses were tested (Gelweave™; Group G, J Graft SHIELD NEO^®; Group J and Triplex^®; Group T). Prostheses were implanted into Sprague-Dawley rats subcutaneously or sutured on abdominal aorta of Japanese white rabbits. The tissues were surgically examined for adhesion and were subjected to histological evaluations for cellular and tissue infiltration and ultrastructural observations by scanning electron microscopy (SEM). Group G exhibited less tendency in adhesion formation in early phase (rat: G vs J, P < 0.0001; G vs T, P < 0.0001/rabbit: G vs J, P < 0.0001; G vs T, P = 0.059). In late phase, Group J showed highest adhesion (rat: G vs J, P = 0.0004; J vs T, P = 0.015/rabbit: G vs J, P = 0.0015; J vs T, P = 0.0044). In group G, a gap was observed between implants and surrounding tissues forming capsulation, whereas other groups exhibited tissue infiltration inside of the implants wall which were also confirmed by SEM. The tissue permeation toward the implants and adhesion was positively correlated (P < 0.0001). Surrounding tissue conformation varied in accordance with the type of prostheses. It is desirable to elucidate characteristics of each prosthesis to select suitable grafts for each patient to achieve a better surgical outcome.

Novel device prototyping for endoscopic cell sheet transplantation using a three-dimensional printed simulator

Introduction

Considering higher risks of candidates for cardiac regenerative therapy with compromised cardiac function, it is anticipated to develop less invasive surgical procedures. In the present study, we aimed to develop a prototype of totally endoscopic cell sheet delivery device and evaluate the surgical technique for epicardial cell sheet placement using three-dimensional (3D) printed simulators based on human computed tomography data.

Methods

We designed an endoscopic cell sheet delivery device with outer and inner frame with self-expandable applicator which can be opened in thoracic cavity. We launched spout line to provide liquids on the applicator surface and tension line to gently bend the applicator dorsally. We prepared human mesenchymal stem cell (MSC) sheets and compared wet/dry conditions of 3D printed heart/porcine heart and applicator to identify suitable conditions for cell sheet transplantation. Finally we validated the feasibility of endoscopic transplantation to anterior and lateral wall of left ventricle using 3D printed simulators.

Results

Moist condition of both 3D printed heart/porcine heart surface and applicator at transplantation yielded highest successful rate (100%, p = 0.0197). For both endoscopic transplantation sites, MSC sheets were successfully deployed. The procedure duration was 157 ± 23 s for anterior wall and 123 ± 13 s for the lateral wall in average, respectively.

Conclusions

We developed a novel prototype of endoscopic cell sheet delivery device for minimally-invasive cardiac regenerative therapy utilizing a 3D printed simulator. The commercialization of the prototype may provide a safe minimally-invasive method to deliver potential cardiac regenerative therapy in the future.

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We invented a novel device for endoscopic cell sheet transplantation.

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We optimized the transplantation procedure using three-dimensional printed simulator.

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Commercialization of the device may provide standardized cardiac regenerative therapy.

Management of retrosternal adhesion after median sternotomy by controlling degradation speed of a dextran and ε-poly (L-lysine)-based biocompatible glue

OBJECTIVE

Retrosternal adhesion after median sternotomy possibly raises the risk of cardiac injury at resternotomy. A biodegradable glue "Lydex" is composed of food additives, dextran and ε-poly (L-lysine), and the degradation speed can be controlled by the composition. In the present study, we evaluated the preventative effect of Lydex on retrosternal adhesion and the relationship between degradation speed and the progression of retrosternal fibrosis.

METHODS

Japanese white rabbits are subjected to median sternotomy. Lydex 1, 2 and 3 were loaded at the retrosternal space of rabbits in allocated groups before sternal closure, respectively (n = 11 for each group). Retrosternal adhesion was macroscopically evaluated after surgery. Retainment of Lydex, retrosternal fibrosis and the infiltration of macrophages are histologically evaluated, respectively.

RESULTS

All Lydex groups exhibited less retrosternal adhesion at 4 weeks after loading compared to unloaded control. The degradation speed of Lydex varied according to the compositions. Lydex with faster degradation (Lydex 2 or Lydex 3) showed lower progression of retrosternal fibrosis compared to that with slower degradation (Lydex 1) [fibrosis ratio: control vs Lydex 1 vs Lydex 2 vs Lydex 3: 0.60 ± 0.15 vs 0.18 ± 0.17 vs 0.00 ± 0.00 vs 0.00 ± 0.00, P = 0.0005 (Lydex 1 vs Lydex 2), P = 0.0005 (Lydex 1 vs Lydex 3)]. Retrosternal infiltrations of macrophages in Lydex 1 and Lydex 3 groups are not higher compared to that in unloaded control.

CONCLUSIONS

The degradation speed of Lydex could be controlled according to the compositions. The degradation speed affected the progression of retrosternal fibrosis.