Improved hydration property of tissue adhesive/hemostatic microparticle based on hydrophobically-modified Alaska pollock gelatin.

The management of bleeding is an important aspect of endoscopic surgery to avoid excessive blood loss and minimize pain. In clinical settings, sprayable hemostatic particles are used for their easy delivery, adaptability to irregular shapes, and rapid hydration. However, conventional hemostatic particles present challenges associated with tissue adhesion. In a previous study, we reported tissue adhesive microparticles (C10-sa-MPs) derived from Alaska pollock gelatin modified with decyl groups (C10-sa-ApGltn) using secondary amines as linkages. The C10-sa-MPs adhere to soft tissues through a hydration mechanism. However, their application as a hemostatic agent was limited by their long hydration times, attributed to their high hydrophobicity. In this study, we present a new type microparticle, C10-am-MPs, synthesized by incorporating decanoyl group modifications into ApGltn (C10-am-ApGltn), using amide bonds as linkages. C10-am-MPs exhibited enhanced hydration characteristics compared to C10-sa-MPs, attributed to superior water absorption facilitated by amide bonds rather than secondary amines. Furthermore, C10-am-MPs demonstrated comparable tissue adhesion properties and underwater adhesion stability to C10-sa-MPs. Notably, C10-am-MPs exhibited accelerated blood coagulation in vitro compared to C10-sa-MPs. The application of C10-am-MPs in an in vivo rat liver hemorrhage model resulted in a hemostatic effect comparable to a commercially available hemostatic particle. These findings highlight the potential utility of C10-am-MPs as an effective hemostatic agent for endoscopic procedures and surgical interventions.

Enhanced ROS scavenging and tissue adhesive abilities in injectable hydrogels by protein modification with oligoethyleneimine.

Postsurgical treatment comprehensively benefits from the application of tissue-adhesive injectable hydrogels, which reduce postoperative complications by promoting wound closure and tissue regeneration. Although various hydrogels have been employed as clinical tissue adhesives, many exhibit deficiencies in adhesive strength under wet conditions or in immunomodulatory functions. Herein, we report the development of reactive oxygen species (ROS) scavenging and tissue-adhesive injectable hydrogels composed of polyamine-modified gelatin crosslinked with the 4-arm poly (ethylene glycol) crosslinker. Polyamine-modified gelatin was particularly potent in suppressing the secretion of proinflammatory cytokines from stimulated primary macrophages. This effect is attributed to its ability to scavenge ROS and inhibit the nuclear translocation of nuclear factor kappa-B. Polyamine-modified gelatin-based hydrogels exhibited ROS scavenging abilities and enhanced tissue adhesive strength on collagen casing. Notably, the hydrogel demonstrated exceptional tissue adhesive properties in a wet environment, as evidenced by its performance using porcine small intestine tissue. This approach holds significant promise for designing immunomodulatory hydrogels with superior tissue adhesion strength compared to conventional medical materials, thereby contributing to advancements in minimally invasive surgical techniques.

Elucidation of prognostic factors in the acute phase of feline severe fever with thrombocytopenia syndrome virus infection.

Severe fever with thrombocytopenia syndrome (SFTS) is a potentially fatal tick-borne zoonotic disease, endemic to Asian regions, including western Japan. Cats appear to suffer a particularly severe form of the disease; however, feline SFTS is not clinically well characterized. Accordingly, in this study, we investigated the associations of, demographic, hematological and biochemical, immunological, and virological parameters with clinical outcome (fatal cases vs. survivors) in SFTSV-positive cats. Viral genomic analysis was also performed. Viral load in blood, total bilirubin, creatine phosphokinase, serum amyloid A, interleukin-6, tumor necrotic factor-α, and virus-specific IgM and IgG differed significantly between survivors and fatal cases, and thus may have utility as prognosticators. Furthermore, survivor profiling revealed high-level of viremia with multiple parameters (white blood cells, platelet, total bilirubin, glucose, and serum amyloid A) beyond the reference range in the 7-day acute phase, and signs of clinical recovery in the post-acute phase (parameters returning to, or tending toward, the reference range). However, SFTSV was still detectable from some survived cats even 14 days after onset of disease, indicating the risk of infection posed by close-contact exposure may persist through the post-acute phase. This study provides useful information for prognostic assessments of acute feline SFTS, and may contribute to early treatment plans for cats with SFTS. Our findings also alert pet owners and animal health professionals to the need for prolonged vigilance against animal-to-human transmission when handling cats that have been diagnosed with SFTS.

Injectable microcapillary network hydrogels engineered by liquid-liquid phase separation for stem cell transplantation.

Injectable hydrogels are promising carriers for cell delivery in regenerative medicine. However, injectable hydrogels composed of crosslinked polymer networks are often non-microporous and prevent biological communication with host tissues through signals, nutrients, oxygen, and cells, thereby limiting graft survival and tissue integration. Here we report injectable hydrogels with liquid-liquid phase separation-induced microcapillary networks (µCN) as stem cell-delivering scaffolds. The molecular modification of gelatin with hydrogen bonding moieties induced liquid-liquid phase separation when mixed with unmodified gelatin to form µCN structures in the hydrogels. Through spatiotemporally controlled covalent crosslinking and dissolution processes, porous µCN structures were formed in the hydrogels, which can enhance mass transport and cellular activity. The encapsulation of cells with injectable µCN hydrogels improved cellular spreading, migration, and proliferation. Transplantation of mesenchymal stem cells with injectable µCN hydrogels enhanced graft survival and recovered hindlimb ischemia by enhancing material-tissue communication with biological signals and cells through µCN. This facile approach may serve as an advanced scaffold for improving stem cell transplantation therapies in regenerative medicine.

Sprayable tissue adhesive microparticle-magnetic nanoparticle composites for local cancer hyperthermia.

Incomplete removal of early-stage gastrointestinal cancers by endoscopic treatments often leads to recurrence induced by residual cancer cells. To completely remove or kill cancer tissues and cells and prevent recurrence, chemotherapy, radiotherapy, and hyperthermia using biomaterials with drugs or nanomaterials are usually administered following endoscopic treatments. However, there are few biomaterials that can be applied using endoscopic devices to locally kill cancer tissues and cells. We previously reported that decyl group-modified Alaska pollock gelatin-based microparticles (denoted C10MPs) can adhere to gastrointestinal tissues under wet conditions through the formation of a colloidal gel driven by hydrophobic interactions. In this study, we combined C10MPs with superparamagnetic iron oxide nanoparticles (SPIONs) to develop a sprayable heat-generating nanomaterial (denoted SP/C10MP) for local hyperthermia of gastrointestinal cancers. The rheological property, tissue adhesion strength, burst strength, and underwater stability of SP/C10MP were improved through decyl group modification and SPION addition. Moreover, SP/C10MP that adhered to gastrointestinal tissues formed a colloidal gel, which locally generated heat in response to an alternating magnetic field. SP/C10MP successfully killed cancer tissues and cells in colon cancer-bearing mouse models in vitro and in vivo. Therefore, SP/C10MP has the potential to locally kill residual cancer tissues and cells after endoscopic treatments.

Improved Swelling Property of Tissue Adhesive Hydrogels Based on α-Cyclodextrin/Decyl Group-Modified Alaska Pollock Gelatin Inclusion Complexes.

Adhesives/sealants are used after suturing to prevent leakage of cerebrospinal fluid from an anastomotic site. Commercial adhesives/sealants have been used to close the cerebral dura. However, swelling of the cured adhesives/sealants induces increased intracranial pressure and decreases the strength of the seal. In the present study, tissue adhesive hydrogels with improved swelling property using inclusion complex composed of α-cyclodextrin (αCD) and decyl group (C10)-modified Alaska pollock-derived gelatin (C10-ApGltn) with a high degree of substitution (DS) (>20 mol%) are developed. Viscosity of C10-ApGltn with a high DS solution remarkably decreased by the addition of αCD. The resulting αCD/C10-ApGltn adhesive hydrogel composed of αCD/C10-ApGltn inclusion complexes and poly(ethylene glycol) (PEG)-based crosslinker showed improved swelling property after immersion in saline. Also, the resulting adhesive has a significantly higher burst strength than fibrin-based adhesives and is as strong as a PEG-based adhesive. Quantitative analysis of αCD revealed that the improved swelling property of the resulting adhesive hydrogels is induced by the release of αCD from cured adhesive, and the subsequent assembly of decyl groups in the saline. These results suggest that adhesives developed using the αCD/C10-ApGltn inclusion complex can be useful for closing the cerebral dura mater.

Inflammation-targeting polyamine nanomedicines for the treatment of ulcerative colitis.

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder characterized by immune system dysfunction. Despite the availability of various anti-inflammatory drugs, they exhibit low therapeutic efficacy with systemic side effects. In this study, we developed oral anti-inflammatory polyamine-based nanomedicines for the treatment of ulcerative colitis. Polyamine-bearing nanoparticles were prepared by the self-assembly of hyaluronic acid in organic solvents and crosslinking with branched oligoethyleneimine. Polyamine nanoparticles were found to suppress excessive inflammatory responses by scavenging the reactive oxygen species (ROS). Moreover, these nanoparticles inhibited enzymatic degradation and targeting of inflamed intestinal tissues. Additionally, they suppressed the inflammatory responses and recovered the pathological disorders in the colon of an ulcerative colitis mouse model. Therefore, polyamine-based nanomedicines exhibit great potential as biocompatible ROS-scavenging drugs for the treatment of IBD.

Tissue-Adhesive Decellularized Extracellular Matrix Patches Reinforced by a Supramolecular Gelator to Repair Abdominal Wall Defects.

Implantation of surgical meshes composed of synthetic and biological materials has been applied for abdominal wall defect repair. Despite many efforts, there are no reliable meshes that fully satisfy clinical requirements because of their lack of biodegradability, mechanical strength, and tissue-adhesive properties. Here, we report biodegradable, decellularized extracellular matrix (dECM)-based biological patches to treat abdominal wall defects. By incorporating a water-insoluble supramolecular gelator that forms physical cross-linking networks through intermolecular hydrogen bonding, dECM patches were reinforced to improve mechanical strength. Reinforced dECM patches possessed higher tissue adhesion strength and underwater stability compared with the original dECM because of enhanced interfacial adhesion strength. In vivo experiments using an abdominal wall defect rat model showed that reinforced dECM patches induced collagen deposition and the formation of blood vessels during material degradation, and the accumulation of CD68-positive macrophages was suppressed compared to nonbiodegradable synthetic meshes. Tissue-adhesive and biodegradable dECM patches with improved mechanical strength by a supramolecular gelator have enormous potential for use in the repair of abdominal wall defects.

Effect of particle size on the tissue adhesion and particle floatation of a colloidal wound dressing for endoscopic treatments.

Endoscopic submucosal dissection (ESD) is a minimally invasive technique that is widely used to remove gastrointestinal tumors. However, because the walls of the duodenum and large intestine are thin, perforation can easily occur after ESD. We have previously reported that alkyl group-modified Alaska pollock gelatin-based microparticles (C10Ps) formed a colloidal gel that could adhere to defects and close perforations, driven by hydrophobic interactions. The present study focused on the effect of particle size on the colloidal gel properties and the floatation of C10Ps in the air in the delivery of C10Ps. We prepared C10Ps with different particle sizes from 0.1 to 100 µm. The storage modulus and adhesion strength of the C10P colloidal gel increased with decreasing particle size. All the C10Ps formed a colloidal gel layer on duodenum tissue after being sprayed from an endoscopic device. The underwater stability and burst strength of C10Ps with a particle size of 0.1 and 1 µm were higher than for larger C10Ps. Floating of the small-sized C10Ps in the air was observed. The results indicated that C10Ps with a size of 1 µm had suitable properties for use in endoscopic treatments. STATEMENT OF SIGNIFICANCE: We previously reported tissue adhesive microparticles as a spray-deliverable wound dressing in gastrointestinal tissues. However, their functions depending on particle size have not yet been clarified. In the present study, we prepared decyl group-modified Alaska pollock gelatin nano and microparticles (C10Ps) with different particle sizes from 0.1 to 100 µm and evaluated the effect of particle size on the colloidal gel properties (rheological property, underwater stability and perforation-closing ability) and the floatation of C10Ps in the air in the delivery of C10Ps.

Effects of Sprayable, Highly Adhesive Hydrophobized Gelatin Microparticles on Endoscopic Submucosal Dissection: A Swine Model.

INTRODUCTION: Sprayable wound dressings containing hydrophobized microparticles (hMPs) are characterized by strong adhesiveness. We examined the effect of hMPs derived from Alaska pollock gelatin on endoscopic submucosal dissection (ESD) ulcers. METHODS: (1) In an in vivo model of miniature swine gastric ESD, gastric ulcers were created by ESD and then sprayed with hMPs or untreated followed by microscopic examination. (2) In an ex vivo ESD model of resected stomach, a pinhole-shaped perforation was created on the ESD ulcer of resected stomach; hMPs were then sprayed on the perforation; and air leakage and intragastric pressure were measured. (3) In an in vivo duodenal ESD model of miniature swine, duodenal artificial ESD ulcers with pinhole-shaped perforation were examined; ulcers were classified into hMPs-sprayed and nonsprayed groups, and inflammation in the intrinsic muscle layer and serosa were compared between the groups. RESULTS: (1) Histological observation of submucosal tissues showed a decreased number of invading inflammatory cells in hMP-sprayed tissues compared with the control in miniature swine gastric ESD (p < 0.05). In addition, the rates of anti-alpha smooth muscle actin and type I collagen positivity were significantly lower in the hMPs group than in the control group (p < 0.05). (2) Intragastric pressure could not be measured in the nonsprayed group, whereas no air leakage was observed in the sprayed group when pressurized up to 26 mm Hg in the resected stomach model. (3) The sprayed group showed suppressed inflammation of the intrinsic muscular layer and serosa in both cases compared with the nonsprayed group in miniature swine duodenal ESD (p < 0.05). CONCLUSIONS: Sprayable, tissue-adhesive hMPs are a promising medical material for intraoperative and postoperative treatment of ESD-induced wound via anti-inflammation and strong adhesiveness.

Engineering thixotropic supramolecular gelatin-based hydrogel as an injectable scaffold for cell transplantation.

Despite many efforts focusing on regenerative medicine, there are few clinically-available cell-delivery carriers to improve the efficacy of cell transplantation due to the lack of adequate scaffolds. Herein, we report an injectable scaffold composed of functionalized gelatin for application in cell transplantation. Injectable functionalized gelatin-based hydrogels crosslinked with reversible hydrogen bonding based on supramolecular chemistry were designed. The hydrogel exhibited thixotropy, enabling single syringe injection of cell-encapsulating hydrogels. Highly biocompatible and cell-adhesive hydrogels provide cellular scaffolds that promote cellular adhesion, spreading, and migration. Thein vivodegradation study revealed that the hydrogel gradually degraded for seven days, which may lead to prolonged retention of transplanted cells and efficient integration into host tissues. In volumetric muscle loss models of mice, cells were transplanted using hydrogels and proliferated in injured muscle tissues. Thixotropic and injectable hydrogels may serve as cell delivery scaffolds to improve graft survival in regenerative medicine.

Enhanced burst strength of catechol groups-modified Alaska pollock-derived gelatin-based surgical adhesive.

Aortic anastomotic leak is a potentially fatal complication that can occur after treatment of aortic dissection or aneurysm. Several surgical adhesives have been used to prevent this complication, but all have problems with regard to tissue adhesion or biocompatibility. In the present study, we developed a surgical adhesive composed of boric acid-protected catechol groups-modified Alaska pollock-derived gelatin (Cat-ApGltn) and a poly(ethylene glycol)-based crosslinker (4S-PEG). By avoiding oxidation of catechol groups using boric acid, resulting Cat-ApGltn adhesive formed a strong hydrogel by double crosslinking: chemical crosslinking by 4S-PEG, and chemical and physical crosslinking by the catechol groups. The catechol groups modification contributed to increased bulk strength and decreased gelation time/swelling ratios. The Cat-ApGltn adhesive, in which 7.8 mol% of the amino groups of the original ApGltn (Org-ApGltn) were modified with catechol groups, demonstrated 2.3 times higher burst strength compared with the Org-ApGltn adhesive, and 3.9 times higher burst strength compared with a commercial fibrin adhesive. When the Cat-ApGltn adhesive was implanted subcutaneously into rats, it induced only weak inflammation similar to that induced by the Org-ApGltn adhesive, and was completely degraded within 2 months. Therefore, the Cat-ApGltn adhesive has great potential for use in the field of cardiovascular surgery.

Liquid-Liquid Phase-Separated Hydrogel with Tunable Sol-Gel Transition Behavior as a Hotmelt-Adhesive Postoperative Barrier.

Postoperative barriers have been widely used to prevent adhesions. However, there are currently few barriers that satisfy clinical requirements, such as tissue adhesion, operability, and biocompatibility. Inspired by the adhesion system of living organisms, we report a liquid-liquid phase-separated hydrogel as a single-syringe hotmelt-type postoperative barrier. Mixing polyethylene glycol with gelatin formed liquid-liquid phase-separated hydrogels through segregative liquid-liquid phase separation. Incorporation of a liquid-liquid phase-separated system into gelatin can enhance the sol-gel transition temperature to give a hotmelt-adhesive property to hydrogels. Hotmelt-adhesive hydrogels became a sol phase and cohered into tissue gaps when warmed and solidified at body temperature to adhere to soft tissues. The hydrogels exhibited tissue adhesion to large intestine tissues and showed improved mechanical strength, gelation time, and shear-thinning properties. In rat cecum-abdominal adhesion models, it was confirmed that the resulting hydrogels prevented abdominal adhesion and did not prevent tissue regeneration. Hotmelt-adhesive hydrogels with high tissue adhesive properties, operability, and biocompatibility have enormous potential as barriers to prevent postoperative complications.

Prevention of postoperative adhesion with a colloidal gel based on decyl group-modified Alaska pollock gelatin microparticles.

Postoperative adhesion, bonding of the abdominal wall to damaged organs, causes severe complications after abdominal surgery. Despite the availability of physical barriers (i.e., solutions, films, and hydrogels), adhesion prevention materials that are a single-substance system with stability in wet tissue and ease of use have not been reported. Here, we report a microparticle based, sprayable adhesion prevention material comprising decyl group modified Alaska pollock gelatin (C10-ApGltn). C10-ApGltn microparticles (C10-MPs) were prepared by a coacervation method, freeze drying, and thermal crosslinking. The C10-MPs adhered to and formed a colloidal gel layer on intestinal serosal tissue by hydration without any crosslinking agents. After hydration of the C10-MPs, the resulting colloidal gel layer did not adhere to other tissues. Additionally, the C10-MP colloidal gel layer formed on the stomach serosal tissue showed stability when submersed in saline for 2 days. The colloidal gel layer also showed tissue followability. An in vivo rat adhesion model revealed that C10-MP colloidal gel layer on the cecum and abdominal wall defects effectively reduced postoperative adhesion and induced tissue remodeling, including re-mesothelialization. Therefore, C10-MPs are a potential anti-adhesion material for preventing postoperative adhesion. STATEMENT OF SIGNIFICANCE: We evaluated the postoperative adhesion prevention ability of a colloidal gel based on decyl group modified Alaska pollock gelatin (ApGltn) microparticles (C10-MPs). These microparticles are sprayable and form a colloidal gel with only hydration on the gastrointestinal tissue. We revealed that the modification of the decyl group into ApGltn improved the stability of C10-MP colloidal gel on the tissue by hydrophobic interaction in the in-vitro experiments. The gel prevented postoperative adhesion by being a physical barrier in the in-vivo rat adhesion model.

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.

A Trade-off Between Thermostability and Binding Affinity of Anti-(4-hydroxy-3-nitrophenyl)Acetyl Antibodies During the Course of Affinity Maturation.

Somatic hypermutation (SHM) is one of the driving forces that increases antibody (Ab) affinity. We studied the effects of SHM on thermostability and affinity using three single-chain Fv fragments (scFvs) of anti-(4-hydroxy-3-nitrophenyl)acetyl Abs, namely 9TG, 9T7, and E11. 9TG has a germline structure that lacks SHM and is an ancestor of 9T7 with 11 mutations. E11, which has 21 mutations, is a mature Ab and has its own ancestor. The thermostabilities and antigen-Ab interactions were analyzed by circular dichroism (CD), differential scanning calorimetry (DSC), and isothermal titration calorimetry (ITC). Far-UV CD spectra showed that all scFvs were folded into a structure referred to as immunoglobulin-fold and were unfolded by heating at different melting temperatures. Comparison of thermodynamic parameters obtained from DSC and ITC revealed that the magnitude of stabilization free energy at 37 °C was in the order, 9TG > 9T7 > E11, while that of the free energy of interaction with antigen was 9TG < 9T7 < E11, suggesting that Abs make a trade-off between stability and affinity during affinity maturation.

Fabrication of highly stretchable hydrogel based on crosslinking between alendronates functionalized poly-γ-glutamate and calcium cations.

We report a highly stretchable hydrogel based on the crosslinking structure between calcium cations and alendronates (ALN) conjugated with poly-γ-glutamate (γ-PGA), a typical biodegradable polymer. γ-PGA with ALN (γ-PGA-ALN) forms the hydrogel in the aqueous solution containing CaCl2. The hydrogel shows 2000% of stretchability and reversible stretching without failure at a strain of 250%. The fracture strain and stress are tunable by varying the concentration of either γ-PGA-ALN or CaCl2, indicating the importance of fine-tuning of the density of the cross-linkage to control the mechanical properties of the hydrogel. We believe the biodegradable polymer based highly stretchable hydrogel has potential for use in various fields such as tissue engineering.

CXCL12 promotes CCR7 ligand-mediated breast cancer cell invasion and migration toward lymphatic vessels.

Chemokines are a family of cytokines that mediate leukocyte trafficking and are involved in tumor cell migration, growth, and progression. Although there is emerging evidence that multiple chemokines are expressed in tumor tissues and that each chemokine induces receptor-mediated signaling, their collaboration to regulate tumor invasion and lymph node metastasis has not been fully elucidated. In this study, we examined the effect of CXCL12 on the CCR7-dependent signaling in MDA-MB-231 human breast cancer cells to determine the role of CXCL12 and CCR7 ligand chemokines in breast cancer metastasis to lymph nodes. CXCL12 enhanced the CCR7-dependent in vitro chemotaxis and cell invasion into collagen gels at suboptimal concentrations of CCL21. CXCL12 promoted CCR7 homodimer formation, ligand binding, CCR7 accumulation into membrane ruffles, and cell response at lower concentrations of CCL19. Immunohistochemistry of MDA-MB-231-derived xenograft tumors revealed that CXCL12 is primarily located in the pericellular matrix surrounding tumor cells, whereas the CCR7 ligand, CCL21, mainly associates with LYVE-1+ intratumoral and peritumoral lymphatic vessels. In the three-dimensional tumor invasion model with lymph networks, CXCL12 stimulation facilitates breast cancer cell migration to CCL21-reconstituted lymphatic networks. These results indicate that CXCL12/CXCR4 signaling promotes breast cancer cell migration and invasion toward CCR7 ligand-expressing intratumoral lymphatic vessels and supports CCR7 signaling associated with lymph node metastasis.

A Novel Alaska Pollock Gelatin Sealant Shows Higher Bonding Strength and Nerve Regeneration Comparable to That of Fibrin Sealant in a Cadaveric Model and a Rat Model.

BACKGROUND: A novel biocompatible sealant composed of Alaska pollock-derived gelatin (ApGltn) has recently shown good burst strength and biocompatibility in a porcine aorta. The purpose of this study was to investigate the bonding strength and biocompatibility of the ApGltn sealant in transected digital nerves of fresh frozen cadavers and in the sciatic nerves of a rat model. METHODS: Eighty human digital nerves of fresh frozen cadavers were transected for biomechanical traction testing. They were treated with four surgical interventions: (1) suture plus ApGltn sealant; (2) suture; (3) ApGltn sealant; and (4) fibrin sealant. Forty-three sciatic nerves of male Wistar rats were used for functional and histopathologic evaluation. They were treated with six surgical interventions: (1) suture plus ApGltn sealant; (2) suture; (3) ApGltn sealant; (4) fibrin sealant; (5) resection with a 5-mm gap (10 rats per group); and (6) sham operation (three rats). Macroscopic confirmation, muscle weight measurement, and histopathologic findings including G-ratio were examined 8 weeks after the procedure. RESULTS: The maximum failure load of the ApGltn sealant was significantly higher than that of a fibrin sealant (0.22 ± 0.05 N versus 0.06 ± 0.04 N). The maximum failure load of the ApGltn sealant was significantly lower that of suture plus ApGltn sealant (1.37 N) and suture (1.27 N). Functional evaluation and histologic examination showed that sciatic nerves repaired with ApGltn sealant showed similar nerve recovery compared to repair with the suture and fibrin sealant. CONCLUSION: The ApGltn sealant showed higher bonding strength and equal effect of nerve regeneration when compared with the fibrin sealant.

Anisometric Microstructures to Determine Minimal Critical Physical Cues Required for Neurite Alignment.

In nerve regeneration, scaffolds play an important role in providing an artificial extracellular matrix with architectural, mechanical, and biochemical cues to bridge the site of injury. Directed nerve growth is a crucial aspect of nerve repair, often introduced by engineered scaffolds imparting linear tracks. The influence of physical cues, determined by well-defined architectures, has been mainly studied for implantable scaffolds and is usually limited to continuous guiding features. In this report, the potential of short anisometric microelements in inducing aligned neurite extension, their dimensions, and the role of vertical and horizontal distances between them, is investigated. This provides crucial information to create efficient injectable 3D materials with discontinuous, in situ magnetically oriented microstructures, like the Anisogel. By designing and fabricating periodic, anisometric, discreet guidance cues in a high-throughput 2D in vitro platform using two-photon lithography techniques, the authors are able to decipher the minimal guidance cues required for directed nerve growth along the major axis of the microelements. These features determine whether axons grow unidirectionally or cross paths via the open spaces between the elements, which is vital for the design of injectable Anisogels for enhanced nerve repair.