Development of new biodegradable hydrogel glue for preventing alveolar air leakage

Suitable Patient Selection and Optimal Timing of Treatment for Persistent Air Leak after Lung Resection

OBJECTIVES

The choice of therapeutic intervention for postoperative air leak varies between institutions. We aimed to identify the optimal timing and patient criteria for therapeutic intervention in cases of postoperative air leaks after lung resection.

METHODS

This study utilized data from a prospective multicenter observational study conducted in 2019. Among the 2187 cases in the database, 420 cases with air leaks on postoperative day 1 were identified. The intervention group underwent therapeutic interventions, such as pleurodesis or surgery, while the observation group was monitored without intervention. A comparison between the intervention group and the observation group were analyzed using the cumulative distribution and hazard functions.

RESULTS

Forty-six patients (11.0%) were included in the intervention group. The multivariate analysis revealed that low body mass index (p = 0.019), partial resection (p = 0.010), intraoperative use of fibrin glue (p = 0.008), severe air leak on postoperative day 1 (p < 0.001), and high forced expiratory volume in 1 s (p = 0.021) were significant predictors of the requirement for intervention. The proportion of patients with persistent air leak in the observation group was 20% on postoperative day 5 and 94% on postoperative day 7. The hazard of air leak cessation peaked from postoperative day 3 to postoperative day 7.

CONCLUSIONS

This research contributes valuable insights into predicting therapeutic interventions for postoperative air leaks and identifies scenarios where spontaneous cessation is probable. A validation through prospective studies is warranted to affirm these findings.

Evaluating and developing sealants for the prevention of pulmonary air leakage: A systematic review of animal models

Sealants may provide a solution for pulmonary air leakage (PAL), but their clinical application is debatable. For sealant comparison, standardized animal models are lacking. This systematic review aims to assess methodology and quality of animal models for PAL and sealant evaluation. All animal models investigating lung sealing devices (e.g., staplers, glues, energy devices) to prevent or treat PAL were retrieved systematically from Embase, Pubmed and Web of science. Methodological study characteristics, risk of bias, reporting quality and publication bias were assessed. A total of 71 studies were included (N  =  75 experiments, N  =  1659 animals). Six different species and 18 strains were described; 92% of experiments used healthy animals, disease models were used in only six studies. Lesions to produce PAL were heterogenous, and only 11 studies used a previously reported technique, encompassing N  =  5 unique lesions. Clinically relevant outcomes were used in the minority of studies (imaging 16%, air leak 10.7%, air leak duration 4%). Reporting quality was poor, but revealed an upward trend per decade. Overall, high risk of bias was present, and only 18.7% used a negative control group. All but one study without control groups claimed positive outcomes (95.8%), in contrast to 84.3% using positive or negative control groups, which also concluded equivocal, adverse or inconclusive outcomes. In conclusion, animal studies evaluating sealants for prevention of PAL are heterogenous and of poor reporting quality. Using negative control groups, disease models and quantifiable outcomes seem important to increase validity and relevance. Further research is needed to reach consensus for model development and standardization.

Novel external reinforcement device for gastrointestinal anastomosis in an experimental study

BACKGROUND

Anastomotic leakage has been reported to occur when the load on the anastomotic site exceeds the resistance created by sutures, staples, and early scars. It may be possible to avoid anastomotic leakage by covering and reinforcing the anastomotic site with a biocompatible material. The aim of this study was to evaluate the safety and feasibility of a novel external reinforcement device for gastrointestinal anastomosis in an experimental model.

METHODS

A single pig was used in this non-survival study, and end-to-end anastomoses were created in six small bowel loops by a single-stapling technique using a circular stapler. Three of the six anastomoses were covered with a novel external reinforcement device. Air was injected, a pressure test of each anastomosis was performed, and the bursting pressure was measured.

RESULTS

Reinforcement of the anastomotic site with the device was successfully performed in all anastomoses. The bursting pressure was 76.1 ± 5.7 mmHg in the control group, and 126.8 ± 6.8 mmHg in the device group, respectively. The bursting pressure in the device group was significantly higher than that in the control group (p = 0.0006).

CONCLUSIONS

The novel external reinforcement device was safe and feasible for reinforcing the anastomoses in the experimental model.

Safety and performance of surgical adhesives

BACKGROUND

Tissue adhesives are an alternative to conventional surgical sutures to reduce the time and cost of wound closure and to improve patient comfort. The use of tissue adhesives does not require any subsequent intervention and significantly lowers the volume and rate of blood loss, and reduces the need for transfusions during and after surgery. However, based on their formulation, tissue adhesives' safety profile and functional properties may differ. Therefore, this study aimed to evaluate the basic safety and performance of NE'X Glue® Surgical Sealant, BioGlue® Surgical Sealant, and PREVELEAKTM Surgical Sealant in vitro.

METHODS

The basic safety of commercially available tissue adhesives was evaluated using MEM elution assay according to ISO 10993-5 and endotoxin level according to 85. USP. The in vitro performance was evaluated using lap-shear by tension loading test, burst strength test, degradation, and swelling assays.

RESULTS

NE'X Glue®, BioGlue®, and PREVELEAKTM did not cause cytotoxicity in MEM elution assay. All surgical adhesives are below the general limit of endotoxin contamination of 20 EU/device. NE'X Glue® and BioGlue® showed the highest and comparable strength properties in lap shear and burst strength tests compared to PREVELEAKTM. NE'X Glue® and PREVELEAKTM are characterized by lower degradation potential than BioGlue®. PREVELEAKTM is characterized by the highest swelling when compared to NE'X Glue® and BioGlue®.

CONCLUSIONS

NE'X Glue® is most versatile in terms of functional properties while maintaining the same safety profile as BioGlue® and PREVELEAKTM.

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.

Natural polymer-derived photocurable bioadhesive hydrogels for sutureless keratoplasty

Keratoplasty is the gold standard treatment for visual impairment caused by corneal damage. The use of suturing as the bonding method is the source of many complications following keratoplasty. Currently available corneal adhesives do not have both adequate adhesive strength and acceptable biocompatibility. Herein, we developed a photocurable bioadhesive hydrogel which was composed of gelatin methacryloyl and oxidized dextran for sutureless keratoplasty. The bioadhesive hydrogel exhibited high light transmittance, resistance to enzymatic degradation and excellent biocompatibility. It also had higher adhesive strength than commercial adhesives (fibrin glue). In a rabbit model of lamellar keratoplasty, donor corneal grafts could be closely bonded to the recipient corneal bed and remained attached for 56 days by using of this in situ photopolymerized bioadhesive hydrogel. The operated cornea maintained transparent and noninflamed. Sutureless keratoplasty using bioadhesive hydrogel allowed rapid graft re-epithelialization, typically within 7 days. In vivo confocal microscopic and histological evaluation of the operated cornea did not show any apparent abnormalities in terms of corneal cells and ultrastructure. Thus, this bioadhesive hydrogel is exhibited to be an appealing alternative to sutures for keratoplasty and other corneal surgeries.

The Functional Role of Interface Tissue Engineering in Annulus Fibrosus Repair: Bridging Mechanisms of Hydrogel Integration with Regenerative Outcomes

Hydrogels are extraordinarily versatile by design and can enhance repair in diseased and injured musculoskeletal tissues. Biological fixation of these constructs is a significant determinant factor that is critical to the clinical success and functionality of regenerative technologies for musculoskeletal repair. In the context of an intervertebral disc (IVD) herniation, nucleus pulposus tissue protrudes through the ruptured annulus fibrosus (AF), consequentially impinging on spinal nerve roots and causing debilitating pain. Discectomy is the surgical standard of care to treat symptomatic herniation; however these procedures do not repair AF defects, and these lesions are a significant risk factor for recurrent herniation. Advances in tissue engineering utilize adhesive hydrogels as AF sealants; however these repair strategies have yet to progress beyond preclinical animal models because these biomaterials are often plagued by poor integration with AF tissue and lead to large variability in repair outcomes. These critical barriers to translation motivate this article to review the material composition of hydrogels that have been evaluated in situ for AF repair, proposed mechanisms of how these biomaterials interface with AF tissue, and their functional outcomes after treatment in order to inform the development of new hydrogels for AF repair. In this systematic review, we identify 18 hydrogel formulations evaluated for AF repair, all of which demonstrate large heterogeneity in their interfacing mechanisms and reported outcome measures to assess the effectiveness of repair. Hydrogels that covalently bond to AF tissue were found to be the most successful in improving IVD biomechanical properties from the injured state, but none were able to restore properties to the intact state suggesting that new repair strategies with innovative surface chemistries are an important future direction. We additionally review biomechanical evaluation methods and recommend standardization in the field of AF tissue engineering to establish mechanical benchmarks for translation and ensure clinical feasibility.

Engineering Tough, Injectable, Naturally Derived, Bioadhesive Composite Hydrogels

Engineering mechanically robust bioadhesive hydrogels that can withstand large strains may open new opportunities for the sutureless sealing of highly stretchable tissues. While typical chemical modifications of hydrogels, such as increasing the functional group density of crosslinkable moieties and blending them with other polymers or nanomaterials have resulted in improved mechanical stiffness, the modified hydrogels have often exhibited increased brittleness resulting in deteriorated sealing capabilities under large strains. Furthermore, highly elastic hydrogels, such as tropoelastin derivatives are highly expensive. Here, gelatin methacryloyl (GelMA) is hybridized with methacrylate-modified alginate (AlgMA) to enable ion-induced reversible crosslinking that can dissipate energy under strain. The hybrid hydrogels provide a photocrosslinkable, injectable, and bioadhesive platform with an excellent toughness that can be tailored using divalent cations, such as calcium. This class of hybrid biopolymers with more than 600% improved toughness compared to GelMA may set the stage for durable, mechanically resilient, and cost-effective tissue sealants. This strategy to increase the toughness of hydrogels may be extended to other crosslinkable polymers with similarly reactive moieties.

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.

An anti-infective hydrogel adhesive with non-swelling and robust mechanical properties for sutureless wound closure

An anti-infective TA/hydrogel with non-swelling and adhesion properties could close wounds in a non-invasive way.

Controlling the degradation of cellulose scaffolds with Malaprade oxidation for tissue engineering

Cellulose scaffolds, whose biodegradation can be controlled through the reaction with amine compounds in the human body, were developed for tissue engineering applications.

Efficacy of a novel endoscopically deliverable muco-adhesive hemostatic powder in an acute gastric bleeding porcine model

This study investigated the effectiveness of new hemostatic adhesive powder (UI-EWD) in a swine mode of acute gastric bleeding. Gastric ulcer bleeding was induced endoscopically at two locations in each of eight heparinized mini-pigs. UI-EWD and saline were sprayed endoscopically in the experimental (n = 5) and control groups (n = 3), respectively. The hemostatic effect and hydrogel persistence on ulcers were periodically evaluated endoscopically. Initial hemostasis was achieved successfully in all lesions in the experimental group. Follow-up endoscopy showed minor delayed bleeding in 10% at 6 hours in the experimental group, whereas re-bleeding was observed in 50% at 6 hours in the control group. UI-EWD gel persisted at 90%, 80%, and 50% of ulcer bases at 6, 18, and 42 hours post-application, respectively. This study suggests that muco-adhesive UI-EWD may be effective in the endoscopic treatment of active ulcer bleeding.

Ocular adhesives: Design, chemistry, crosslinking mechanisms, and applications

Closure of ocular wounds after an accident or surgery is typically performed by suturing, which is associated with numerous potential complications, including suture breakage, inflammation, secondary neovascularization, erosion to the surface and secondary infection, and astigmatism; for example, more than half of post-corneal transplant infections are due to suture related complications. Tissue adhesives provide promising substitutes for sutures in ophthalmic surgery. Ocular adhesives are not only intended to address the shortcomings of sutures, but also designed to be easy to use, and can potentially minimize post-operative complications. Herein, recent progress in the design, synthesis, and application of ocular adhesives, along with their advantages, limitations, and potential are discussed. This review covers two main classes of ocular adhesives: (1) synthetic adhesives based on cyanoacrylates, polyethylene glycol (PEG), and other synthetic polymers, and (2) adhesives based on naturally derived polymers, such as proteins and polysaccharides. In addition, different technologies to cover and protect ocular wounds such as contact bandage lenses, contact lenses coupled with novel technologies, and decellularized corneas are discussed. Continued advances in this area can help improve both patient satisfaction and clinical outcomes.

Anticancer Therapeutic Alginate-Based Tissue Sealants for Lung Repair

Injury to the connective tissue that lines the lung, the pleura, or the lung itself can occur from many causes including trauma or surgery, as well as lung diseases or cancers. To address current limitations for patching lung injuries, to stop air or fluid leaks, an adherent hydrogel sealant patch system was developed, based on methacrylated alginate (AMA) and AMA dialdehyde (AMA-DA) blends, which is capable of sealing damaged tissues and sustaining physiological pressures. Methacrylation of alginate hydroxyl groups rendered the polysaccharide capable of photo-cross-linking when mixed with an eosin Y-based photoinitiator system and exposed to visible green light. Oxidation of alginate yields functional aldehyde groups capable of imine bond formation with proteins found in many tissues. The alginate-based patch system was rigorously tested on a custom burst pressure testing device. Blending of nonoxidized material with oxidized (aldehyde modified) alginates yielded patches with improved burst pressure performance and decreased delamination as compared with pure AMA. Human mesothelial cell (MeT-5A) viability and cytotoxicity were retained when cultured with the hydrogel patches. The release and bioactivity of doxorubicin-encapsulated submicrospheres enabled the fabrication of drug-eluting adhesive patches and were effective in decreasing human lung cancer cell (A549) viability.

Enhanced sealing strength of a hydrophobically-modified Alaska pollock gelatin-based sealant

A novel tissue sealant composed of hydrophobically-modified Alaska pollock gelatin and polyethylene glycol-based crosslinker showed higher sealing effect than commercially available tissue sealant.

Inflammatory response to dextrin-based hydrogel associated with human mesenchymal stem cells, urinary bladder matrix and Bonelike® granules in rat subcutaneous implants

Increasing relevance has been attributed to hydrogels due to their ability to provide an extracellular matrix (ECM)-like environment for cellular adhesion and proliferation, acting as mechanical scaffolds for tissue remodeling or as delivery matrices. In vivo biocompatibility of a hybrid dextrin hydrogel produced from oxidized dextrin and adipic acid dihydrazide and its combinations with human mesenchymal stem cells (hMSCs), ECM from a porcine bladder (urinary bladder matrix) and ceramic granules (Bonelike^®), was evaluated following ISO 10993 after subcutaneous implantation in a rat model. Histological analysis after 3 and 15 d showed typical acute and chronic inflammatory responses, respectively, with a more severe reaction exhibited whenever the ceramic granules were present. However, the dextrin hydrogel was able to stabilize granules in the implant site. Dextrin hydrogel was scored as slight irritant after 3 d, similar to its combination with UBM, and as non-irritant after 15 d. The presence of viable hMSCs in the subcutaneous tissue could be confirmed by the presence of anti-human nuclei antibody (HuNu⁺) cells. The production of growth factors and inflammatory and immunomodulatory cytokines by these cells was also quantified in peripheral blood confirming the successful encapsulation of hMSCs into the hydrogel matrix for cell survival promotion. The presence of hMSCs seemed to modulate the inflammatory response by accelerating its progression when compared to the acellular experimental groups. Dextrin hydrogel has proven to be a biocompatible multifunctional matrix for minimally invasive biomedical procedures, including orthopedic surgeries when associated with bone substitutes and also as a possible encapsulation matrix for cell-based therapies.

Fragmentation of Injectable Bioadhesive Hydrogels Affords Chemotherapeutic Macromolecules

Implantation of drug delivery depots into or proximal to targeted tissue is an effective method to deliver anticancer drugs in a sustained localized manner. Herein, syringe-injectable polydextran aldehyde (PDA)-based bioadhesive gels are prepared that can locally deliver cytotoxins upon their hydrolytic fragmentation. Adhesive gels are formed by mixing doxorubicin (DOX)-functionalized PDA (DOX-PDA) and bovine serum albumin (BSA) using a dual-barrel syringe. Upon mixing and delivery, the DOX-PDA reacts with the cross-linker BSA as well as the extracellular matrix via imine bond formation to define the cohesive and adhesive properties of the gel, respectively. Resulting gels are mechanically rigid (∼10 kPa) and adherent (adhesive stress ∼ 4 kPa). Once formed, the DOX-PDA-BSA gels undergo slow hydrolytic degradation (>2 months) locally releasing free DOX and DOX-PDA as expected. Surprisingly, we found that macromolecules composed of DOX, PDA, and BSA are also released from the bulk material. These DOX-PDA-BSA macromolecules, along with free DOX and DOX-PDA conjugate, are internalized by A549 lung carcinoma cells, resulting in potent cell death.

Elastic sealants for surgical applications

Sealants have emerged as promising candidates for replacing sutures and staples to prevent air and liquid leakages during and after the surgeries. Their physical properties and adhesion strength to seal the wound area without limiting the tissue movement and function are key factors in their successful implementation in clinical practice. In this contribution, the advances in the development of elastic sealants formed from synthetic and natural materials are critically reviewed and their shortcomings are pointed out. In addition, we highlight the applications in which elasticity of the sealant is critical and outline the limitations of the currently available sealants. This review will provide insights for the development of novel bioadhesives with advanced functionality for surgical applications.

Synthesis and properties of temperature-sensitive and chemically crosslinkable poly(ether-urethane) hydrogel

The PEU-MA solutions can gelate at physiological temperature, and be further crosslinked by UV light.

Aldehyded Dextran and ε -Poly(L-lysine) Hydrogel as Nonviral Gene Carrier

Background. The expression term of the gene transfected in cells needs to belong enough inorder to make a gene therapy clinically effective. The controlled release of the transfected gene can be utilized. The new biodegradable hydrogel material created by 20 w/w% aldehyded dextran and 10 w/w% ε-poly(L-lysine) (ald-dex/PLL) was developed. We examined whether it could be as a nonviral carrier of the gene transfer. Methods. A plasmid (Lac-Z) was mixed with ald-dex/PLL. An in vitro study was performed to assess the expression of Lac-Z with X-gal stain after gene transfer into the cultured 293 cells and bone marrow cells. As a control group, PLL was used as a cationic polymer. Results. We confirmed that the transfection efficiency of the ald-dex/PLL had a higher transfection efficiency than PLL in 293 cells (plasmid of 2 μg: ald-dex/PLL 1.1%, PLL 0.23%, plasmid of 16 μg: ald-dex/PLL 1.23%, PLL 0.48%). In bone marrow cells, we confirmed the expression of Lac-Z by changing the quantity of aldehyded dextran. In the groups using ald-dextran of the quantity of 1/4 and 1/12 of PLL, their transfection efficiency was 0.43% and 0.41%, respectively. Conclusions. This study suggested a potential of using ald-dex/PLL as a non-carrier for gene transfer.

Novel powdered anti-adhesion material: preventing postoperative intra-abdominal adhesions in a rat model

BACKGROUND

Although laparoscopic surgery has decreased postoperative adhesions, complications induced by adhesions are still of great concern. The aim of this study was to investigate the anti-adhesive effects of a novel powdered anti-adhesion material that can be applied during laparoscopic surgery in comparison with other anti-adhesion materials.

METHODS

Our novel powdered anti-adhesion material is composed of aldehyde dextran and ε-poly(L-lysine). In 40 male rats, a 2.5×2.0-cm abdominal wall resection and cecum abrasion were performed. The rats were randomized into four groups based on the anti-adhesion treatments: normal saline; Seprafilm(®); Interceed(®); and novel powdered anti-adhesion material. The animals were euthanized on days 7 and 28 to evaluate the adhesion severity, area of adhesion formation, gross appearance, and pathological changes.

RESULTS

The adhesion severities on both days 7 and 28 were significantly lower for all anti-adhesion material groups compared with the normal saline group (p<0.05). Pathologically, all groups showed inflammatory cell infiltration on day 7 and complete regeneration of the peritoneum on day 28.

CONCLUSIONS

Our novel powdered anti-adhesion material was found to be effective for reducing postoperative intra-abdominal adhesions and showed equivalent efficacy to commercial anti-adhesion materials.

Injectable hyaluronic acid-dextran hydrogels and effects of implantation in ferret vocal fold

Injectable hydrogels may potentially be used for augmentation/regeneration of the lamina propria of vocal fold tissue. In this study, hyaluronic acid (HA) and dextran were chemically modified and subsequently crosslinked via formation of hydrazone bonds in phosphate buffer. Swelling ratios, degradation, and compressive moduli of the resulting hydrogels were investigated. It was found that the properties of HA-dextran hydrogels were variable and the trend of variation could be correlated with the hydrogel composition. The biocompatibility of three injectable HA-dextran hydrogels with different crosslinking density was assessed in the vocal fold region using a ferret model. It was found that HA-dextran hydrogels implanted for three weeks stimulated mild foreign-body reactions. Distinct tissue-material interactions were also observed for hydrogels made from different formulations: the hydrogel with the lowest crosslinking density was completely degraded in vivo; while material residues were visible for other types of hydrogel injections, with or without cell penetration into the implantation depending on the hydrogel composition. The in vivo results suggest that the HA-dextran hydrogel matrices can be further developed for applications of vocal fold tissue restoration.

Characterization of star adhesive sealants based on PEG/dextran hydrogels

Swellable PEG amine/dextran aldehyde composite materials are emerging as a controlled, biocompatible tissue adhesive. We explain how preservation of natural tissue amines provides biocompatibility for PEG/dextran that exceeds the stringent, destructive cyanide-based chemistry of cyanoacrylates, and adhere far better than fibrin glue. Strategic variations of material composition allow for the improvement of biocompatibility and adhesion strength. Material variations can be tailored to match the needs of specific tissue beds for an array of clinical applications. PEG/dextran cohesive properties are most responsive to variations in the PEG component (number of arms and solid content), while tissue/material adhesion strength is primarily determined by the number of aldehydes in the dextran.