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Biomedical subjects

Xiao Zheng Shu

Publications and source records attributed to Xiao Zheng Shu.

At least 19 recordsLinked to original sources
PubMed2006

Synthesis and evaluation of injectable, in situ crosslinkable synthetic extracellular matrices for tissue engineering.

Simple and effective biocompatible materials that mimic the natural extracellular matrix (ECM) were developed for a variety of uses in regenerative medicine. These synthetic ECMs (sECMs) were designed to recapitulate the minimal composition required to obtain functional ECMs. The sECM components are crosslinkable in situ, and may be seeded with cells prior to injection in vivo, without compromising either the cells or the recipient tissues. Several sECM compositions were evaluated to establish which formulation would be most beneficial for cell growth and tissue remodeling. Three natural ECM macromonomeric building blocks were employed: hyaluronan (HA), chondroitin sulfate (CS), and gelatin (Gtn). The carboxyl-rich glycosaminoglycans and Gtn were each chemically modified to give the corresponding thiolated dithiopropionylhydrazide (DTPH) derivatives (CS-DTPH, HA-DTPH, and Gtn-DTPH). Different compositions of CS-Gtn and HA-Gtn hydrogels were fabricated by crosslinking the thiolated biomacromonomers with polyethylene glycol diacrylate. Each sECM had high water content (>96%), biologically suitable mechanical properties, and a useful gelation time ( approximately 2-6 min). The bioerosion rates for the sECMs were determined, and a given composition could be selected to meet the requirements of a given clinical application. Both the HA-Gtn and CS-Gtn sECM hydrogels supported cell growth and proliferation with cultured murine fibroblasts in vitro. Moreover, subcutaneous injection of a suspension of murine fibroblasts in each of the two sECM hydrogels into nude mice in vivo resulted in the formation of viable and uniform soft tissue in vivo.

Adjuvants, Immunologic↗
PubMed2006

Reduced postoperative intra-abdominal adhesions using Carbylan-SX, a semisynthetic glycosaminoglycan hydrogel.

OBJECTIVE: To compare the efficacy of crosslinked Carbylan-SX (Carbylan BioSurgery, Inc., Palo Alto, CA) hydrogel films and sprayable gels as physical barriers in reducing postoperative intra-abdominal adhesions in the rat cecum-abdominal wall and rat uterine horn models. DESIGN: Pre-formed crosslinked Carbylan-SX films and sprayable in situ crosslinkable Carbylan-SX gels were evaluated in rat cecum-abdominal wall and rat uterine horn models and compared with commercially available and clinically used Seprafilm. SETTING: University animal research facility. ANIMALS: Female Wistar rats. INTERVENTION(S): Abrasions were made with the foot-pedal-operated Flex-shaft (Dremel, Racine, WI) on both the cecum and abdominal wall (each area 10 mm in diameter) in female rats as one model and on both uterine horns (3 x 10 mm) in female rats as the other model. In each of the two adhesion models, four groups were assigned with eight rats in each group: (1) untreated control, (2) treated with Seprafilm (Genzyme Corporation, Cambridge, MA), (3) treated with preformed Carbylan-SX hydrogel films, and (4) treated with sprayable Carbylan-SX gel. MAIN OUTCOME MEASURE(S): Extent and severity of postoperative adhesions between the cecum and the abdominal wall in rat cecum-abdominal wall model and between the uterine horns in rat uterine horn model. RESULT(S): The Carbylan-SX film and the Carbylan-SX sprayable gel led to fewer adhesions than Seprafilm in both rat adhesion models. Interestingly, a single physical form was not optimal for both models: the Carbylan film was more efficacious in the rat uterine horn model, whereas Carbylan gel gave the best results in the rat cecum-abdominal wall model. CONCLUSION(S): Both Carbylan-SX film and gel were efficacious in reducing postoperative intra-abdominal adhesion formation in rat cecum-abdominal wall and uterine horn models.

Abdomen↗
PubMed2006

Stimulation of in vivo angiogenesis using dual growth factor-loaded crosslinked glycosaminoglycan hydrogels.

Crosslinked, chemically modified hyaluronan (HA) hydrogels pre-loaded with two cytokine growth factors, vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1), were employed to elicit new microvessel growth in vivo, in both the presence and absence of heparin (Hp) in the gels. HA hydrogel film samples were surgically implanted in the ear pinnae of mice, and the ears were harvested at 7 or 14 days post-implantation. Analysis of neovascularization showed that each of the treatment groups receiving an implant, except for HA/Hp at day 14, demonstrated significantly more microvessel density than control ears undergoing surgery but receiving no implant (p<0.015). Treatment groups receiving either Ang-1 alone, or aqueous co-delivery of both Ang-1 and VEGF, were statistically unchanged with time. In contrast, film delivery of both growth factors produced continuing increases in vascularization from day 7 to day 14 in the absence of Hp, but decreases in its presence. However, presentation of both VEGF and Ang-1 in crosslinked HA gels containing Hp generated intact microvessel beds with well-defined borders. The HA hydrogels containing Ang-1+VEGF produced the greatest angiogenic response of any treatment group tested at day 14 (NI=7.44 in the absence of Hp and 4.67 in its presence, where NI is a neovascularization index). Even in the presence of Hp, this had 29% greater vessel density than the next largest treatment group receiving HA/Hp+VEGF (NI=3.61, p=0.04). New therapeutic approaches for numerous pathologies could be notably enhanced by the localized, sustained angiogenic response produced by release of both VEGF and Ang-1 from crosslinked HA films.

Angiopoietin-1↗
PubMed2006

Heparin-regulated release of growth factors in vitro and angiogenic response in vivo to implanted hyaluronan hydrogels containing VEGF and bFGF.

Controlled release of human vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF) from hydrogels composed of chemically modified hyaluronan (HA) and gelatin (Gtn) was evaluated both in vitro and in vivo. We hypothesized that inclusion of small quantities of heparin (Hp) in these gels would regulate growth factor (GF) release over an extended period, while still maintaining the in vivo bioactivity of released GFs. To test this hypothesis, HA, Gtn, and Hp (15 kDa) were modified with thiol groups, then co-crosslinked with poly (ethylene glycol) diacrylate (PEGDA). Either VEGF or bFGF was incorporated into the gels before crosslinking with PEGDA. Release of these GFs in vitro could be sustained over 42 days by less than 1% Hp content, and was found to decrease monotonically with increasing Hp concentration. As little as 0.03% Hp in the gels reduced the released VEGF fraction from 30% to 21%, while 3% Hp reduced it to 19%. Since the minimum Hp concentration capable of effective controlled GF release in vitro was found to be 0.3% (w/w), this concentration was selected for subsequent in vivo experiments. To evaluate the bioactivity of released GFs in vivo, gel samples were implanted into the ear pinnas of Balb/c mice and the resulting neovascularization response measured. In the presence of Hp, vascularization was sustained over 28 days. GF release was more rapid in vitro from gels containing Gtn than from gels lacking Gtn, though unexpectedly, the in vivo neovascularization response to Gtn-containing gels was decreased. Nevertheless significant numbers of neovessels were generated. The ability to stimulate localized microvessel growth at controlled rates for extended times through the release of GFs from covalently linked, Hp-supplemented hydrogels will ultimately provide a powerful therapeutic tool.

Angiogenesis Inducing Agents↗
PubMed2006

Molecular stenting with a crosslinked hyaluronan derivative inhibits collagen gel contraction.

Adult burn wounds, which lack hyaluronan (HA), often undergo excessive tissue remodeling and contraction. In contrast fetal wounds, which contain large amounts of HA, undergo remodeling that culminates in a scarless repair or regeneration. Therefore, adding a HA derivative to burn wounds would better mimic the fetal extracellular matrix and could reduce contraction. To test this hypothesis, we determined the effects of HA and its two derivatives on fibroblast-mediated, collagen gel contraction, an assay widely used to mimic in vivo wound contraction. Interestingly, high molecular weight HA (HMW HA) facilitated collagen gel contraction, whereas a thiol-functionalized derivative HA-DTPH weakly inhibited contraction. In contrast, polyethylene glycol diacrylate (PEGDA)-crosslinked HA-DTPH (HA-DTPH-PEGDA) strongly inhibited contraction in a concentration-dependent manner. Immunofluorescence staining of cellular actin showed that this inhibition was not owing to reduced cell attachment or spreading. Furthermore, the supernatant of contracted collagen-HMW HA gels contained greater amounts of HA than those found in the supernatant of collagen-HA-DTPH-PEGDA gels, suggesting that HMW HA facilitates contraction by effectively diffusing out of the collagen gels. Therefore, the results suggest that the crosslinking of HA-DTPH enhances the structural mechanics of collagen/HA-DTPH composites, which resists the fibroblast contractile forces and may, therefore, be able to reduce excessive wound contraction observed in pathological conditions.

Adult↗
PubMed2006

Electrospun three-dimensional hyaluronic acid nanofibrous scaffolds.

A three-dimensional (3D) hyaluronic acid (HA) nanofibrous scaffold was successfully fabricated to mimic the architecture of natural extracellular matrix (ECM) based on electrospinning. Thiolated HA derivative, 3,3'-dithiobis(propanoic dihydrazide)-modified HA (HA-DTPH), was synthesized and electrospun to form 3D nanofibrous scaffolds. In order to facilitate the fiber formation during electrospinning, Poly (ethylene oxide) (PEO) was added into the aqueous solution of HA-DTPH at an optimal weight ratio of 1:1. The electrospun HA-DTPH/PEO blend scaffold was subsequently cross-linked through poly (ethylene glycol)-diacrylate (PEGDA) mediated conjugate addition. PEO was then extracted in DI water to obtain an electrospun HA-DTPH nanofibrous scaffold. NIH 3T3 fibroblasts were seeded on fibronectin-adsorbed HA-DTPH nanofibrous scaffolds for 24h in vitro. Fluorescence microscopy and laser scanning confocal microscopy revealed that the 3T3 fibroblasts attached to the scaffold and spread, demonstrating an extended dendritic morphology within the scaffold, which suggests potential applications of HA-DTPH nanofibrous scaffolds in cell encapsulation and tissue regeneration.

Animals↗
PubMed2006

Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrix.

Injectable hydrogel and porous sponge formulations of Carbylan-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with Carbylan-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The Carbylan-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the Carbylan-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. Carbylan-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing.

Animals↗
PubMed2006

Cross-linked hyaluronan-coated stents in the prevention of airway stenosis.

OBJECTIVE: This project studies the use of airway stents coated with a cross-linked derivative of hyaluronan (HA) in a rabbit airway model of subglottic stenosis (SGS). STUDY DESIGN AND SETTING: An acute subglottic mucosal injury and airway stent placement design were used in a rabbit model. Thirty-six rabbits were randomized to 6 different study groups. Four groups had the subglottic mucosa denuded at the cricoid, and 2 groups received no injury. Airway stents coated with Carbylan-SX, a cross-linked derivative of HA, and controls were placed for 3 weeks. After sacrifice at 6 weeks, morphometric measurements of subglottic lumen were taken. RESULTS: In posttraumatic models, no significant differences were seen in airway area measures between groups (P = 0.86). In non-injury groups, a significant difference between Carbylan-SX versus non-HA-derivative-coated stents was seen (P = 0.05). CONCLUSION: In this model of acute subglottic mucosal injury, the HA-derivative-coated stent did not improve healing. However, in the absence of mucosal injury, the Carbylan-SX film-coated stent yielded significantly larger airway areas compared with a noncoated stent. SIGNIFICANCE: Stents or endotracheal tubes coated with a cross-linked derivative of HA may prevent stenosis in patients without airway injury but require long-term intubation or laryngotracheal stenting.

Acute Disease↗
PubMed2006

Crosslinked hydrogels for tympanic membrane repair.

PROBLEM: To provide a less expensive and more convenient protocol for the treatment of tympanic membrane perforations (TMPs). METHODS: Several materials were prepared and compared for TMP repair including Carbylan-SX, Gelatin-DTPH-PEGDA (GX), Carbylan-S/Gelatin-DTPH (Carbylan-GSX) (injectable and sponge), Gelfoam, Epifilm, and crosslinked thiolated chondroitin sulfate (CS-DTPH-PEGDA [CS-SX]). Hartley pigmented guinea pigs (Elm Hill) underwent bilateral myringotomy with 1 ear left as a control and the other treated with one of the previously mentioned materials. RESULTS: Carbylan-GSX (injectable and sponge), Gelfoam with saline, and CS-SX had the shortest time for TMP closure. Epifilm, Carbylan, and gelatin preparations resulted in closure rates similar to controls. CS-SX showed a marked inflammatory reaction compared with controls and other materials based on neutrophil, lymphocyte, epitheloid counts, and degree of fibrosis. CONCLUSIONS: This study shows the validity of Carbylan-GSX compared with Gelfoam as a material to promote TMP closure in an acute TMP guinea pig model.

Animals↗
PubMed2006

Aminooxy pluronics: synthesis and preparation of glycosaminoglycan adducts.

Novel biomaterials have been prepared in which glycosaminoglycans (GAGs) are chemically modified to create amphiphilic multiblock copolymers that are able to adhere to hydrophobic surfaces and can self-assemble into cross-linker-free hydrogels. First, the triblock poly(ethylene oxide)-polypropylene oxide copolymers (Pluronics) were converted into the previously unknown aminooxy (AO) derivatives. Both mono-AO and bis-AO Pluronics (AOPs) were synthesized and fully characterized in order to prepare tetrablock and pentablock copolymers, respectively. Second, the AOPs were coupled to the uronic acid carboxylates of heparin (HP) and hyaluronic acid (HA) using carbodiimide chemistry in order to give the previously undescribed amidooxy GAG derivatives. The coupling chemistry was confirmed using a newly prepared fluorescent AO reagent. Third, AOP-heparin and AOP-fluorescently labeled heparin were shown to adsorb efficiently to polystyrene surfaces, as determined by IL-8 based ELISA and fluorescence measurements, respectively. Fourth, AOP-linked fluorescently labeled HA was shown to adsorb efficiently to plastic surfaces. Finally, three different AOPs were evaluated for self-assembling hydrogel formation by AOP-HA pentablock polymers. In short, AOP-GAG adducts are semisynthetic amphiphilic biomacromolecules that offer a range of valuable practical opportunities for surface modification, preparation of cross-linker-free hydrogels, and formation of self-assembling mimics of the extracellular matrix.

Carbodiimides↗
PubMed2006

Vocal fold tissue repair in vivo using a synthetic extracellular matrix.

Chemically modified hyaluronic acid (HA)-gelatin hydrogels have been documented to support attachment, growth, and proliferation of fibroblasts in vitro and to facilitate repair and engineering of tissues in vivo. The objective of this study was to determine the optimal composition of a synthetic extracellular matrix (sECM) that would promote wound repair and induce tissue regeneration in a rabbit vocal fold wound healing model. The sECM was formed using a thiol-modified semisynthetic glycosaminoglycan (GAG) derived of HA (Carbylan-SX) mixed with a thiolated gelatin derivative, co-cross-linked with poly(ethylene glycol) diacrylate to form Carbylan-GSX. Forty rabbits underwent vocal fold biopsy bilaterally. Rabbits were treated with Carbylan-SX, which lacks gelatin, or with Carbylan-GSX with different gelatin concentrations (2.5%, 5%, 10%, and 20%) via unilateral injection of the vocal fold at the time of biopsy. Saline was injected in the contralateral vocal fold as a control. Three weeks after biopsy and injection, animals were euthanized and mRNA levels of procollagen type 1, fibronectin, transforming growth factor beta 1 (TGF-beta1), fibromodulin, HA synthase 2, hyaluronidase 2, and tissue biomechanics were evaluated. Hyaluronidase mRNA levels were found to be significantly elevated in for Carbylan-GSX 20% w/w gelatin compared to controls. Both Carbylan-SX and Carbylan-GSX significantly improved tissue elasticity and viscosity. Carbylan-GSX containing 5% w/w gelatin showed the most promise as a scaffold material for vocal fold tissue regeneration.

Animals↗
PubMed2006

Fibronectin functional domains coupled to hyaluronan stimulate adult human dermal fibroblast responses critical for wound healing.

Fibronectin (FN) facilitates dermal fibroblast migration during normal wound healing. Proteolytic degradation of FN in chronic wounds hampers healing. Previously, three FN functional domains (FNfd) have been shown to be sufficient for optimal adult human dermal fibroblast migration. Here we report the development of an acellular hydrogel matrix comprised of the FNfds coupled to a hyaluronan (HA) backbone to stimulate wound repair. Employing Michael-type addition, the cysteine- tagged FNfds were first coupled to a homobifunctional PEG derivative. Thereafter, these PEG derivative FNfd solutions, containing bifunctional PEG-derivative crosslinker were coupled to thiol-modified HA (HA-DTPH) to obtain a crosslinked hydrogel matrix. When evaluated in vitro, these acellular hydrogels were completely cytocompatible. While spreading and proliferation of adult human dermal fibroblasts plateaued at higher FNfd bulk densities, their rapid and robust migration followed a typical bell-shaped response. When implanted in porcine cutaneous wounds, these acellular matrices, besides being completely biocompatible, induced rapid and en masse recruitment of stromal fibroblasts that was not observed with RGD-tethered or unmodified hydrogels. Such constructs might be of great benefit in clinical settings where rapid formation of new tissue is needed.

Adult↗
PubMed2006

Cross-linked hydrogels for middle ear packing.

OBJECTIVE: To develop an ideal supportive packing material for ossiculoplasty, tympanoplasty, or other otologic procedures. MATERIALS AND METHODS: Several materials, namely, Carbylan-SX (P-C; Sentrx Surgical, Inc., Salt Lake City, UT), Gelfoam (P-GF; Pharmacia & Upjohn, Kalamazoo, MI), and Merogel (P-MG; Medtronics, Inc., Minneapolis, MN), were prepared and then placed into a Hartley guinea pig's (Elm Hill, Chelmsford, MA) middle ear cavities through a large myringotomy incision. The contralateral ear underwent a large myringotomy without packing material being placed. Preoperative and posteroperative auditory brainstem response studies were performed using Intelligent Hearing system software. The animals were examined weekly. Two weeks after packing placement, the animals were killed, and the temporal bones were harvested. Whole temporal bone sectioning was performed to analyze the presence of implant, surrounding inflammation, presence of osteoneogenesis and fibrosis, or adhesions. RESULTS: All the materials, except the P-MG, were easy to place into the middle ear cavity. The P-MG contains woven strands that are difficult to trim into the small sizes needed for placement. The P-MG group had a smaller average amount of implant present compared with the other groups at 2 weeks. The degree of osteoneogenesis was similar among the P-GF, P-C, and P-MG groups. The P-MG and P-C groups contained the lowest amount of fibrosis between the implant and surrounding middle ear structures. CONCLUSION: This study demonstrates promising results with P-C as a potential supportive packing material for otologic procedures. P-C compares favorably with P-MG and P-GF in a guinea pig model with respect to ease of placement and amount of fibrosis.

Animals↗
PubMed2005

Dual growth factor-induced angiogenesis in vivo using hyaluronan hydrogel implants.

Crosslinked hyaluronan (HA) hydrogels preloaded with two cytokine growth factors, vascular endothelial growth factor (VEGF) and keratinocyte growth factor (KGF), were employed to elicit new microvessel growth in vivo. As a major glycosaminoglycan (GAG) component of extracellular matrix (ECM), HA is an excellent biopolymeric building block for new biomimetic, biocompatible therapeutic materials. HA hydrogel film samples were surgically implanted in the ear pinnae of mice, and the ears were harvested at 7 or 14 days post-implantation. Histologic analysis showed that each of the groups receiving an implant demonstrated significantly more microvessel density than control ears undergoing surgery but receiving no implant (p<0.001). Treatment groups receiving either co-delivery of both KGF and VEGF, an HA hydrogel lacking a growth factor or HA hydrogels containing a single cytokine were statistically unchanged with time, whereas treatment with KGF alone produced continuing increases in vascularization from day 7 to day 14. Strikingly, presentation of both VEGF and KGF in crosslinked HA generated intact microvessel beds with well-defined borders. In addition, an additive response to co-delivery of both cytokines in the HA hydrogel was observed. The HA hydrogels containing KGF+VEGF produced the greatest angiogenic response of any treatment group tested (NI=5.4 at day 14, where NI is a neovascularization index). This was 33% greater vessel density than in the next largest treatment group, that received HA+KGF (NI=4.0, p<0.002). New therapeutic approaches for numerous pathologies could be notably enhanced by the localized, sustained angiogenic response produced by release of both VEGF and KGF from crosslinked HA films.

Angiogenesis Inducing Agents↗
PubMed2005

Injectable glycosaminoglycan hydrogels for controlled release of human basic fibroblast growth factor.

Synthetic hydrogel mimics of the extracellular matrix (ECM) were created by crosslinking a thiol-modified analog of heparin with thiol-modified hyaluronan (HA) or chondroitin sulfate (CS) with poly(ethylene glycol) diacrylate (PEGDA). The covalently bound heparin provided a crosslinkable analog of a heparan sulfate proteoglycan, thus providing a multivalent biomaterial capable of controlled release of basic fibroblast growth factor (bFGF). Hydrogels contained >97% water and formed rapidly in <10min. With as little as 1% (w/w) covalently bound heparin (relative to total glycosaminoglycan content), the rate of release of bFGF in vitro was substantially reduced. Total bFGF released increased with lower percentages of heparin; essentially quantitative release of bFGF was observed from heparin-free hydrogels. Moreover, the hydrogel-released bFGF retained 55% of its biological activity for up to 28 days as determined by a cell proliferation assay. Finally, when these hydrogels were implanted into subcutaneous pockets in Balb/c mice, neovascularization increased dramatically with HA and CS hydrogels that contained both bFGF and crosslinked heparin. In contrast, hydrogels lacking bFGF or crosslinked heparin showed little increase in neovascularization. Thus, covalently linked, heparin-containing glycosaminoglycan hydrogels that can be injected and crosslinked in situ constitute highly promising new materials for controlled release of heparin-binding growth factors in vivo.

Animals↗
PubMed2005

Biocompatibility and stability of disulfide-crosslinked hyaluronan films.

Hyaluronan (HA) can be chemically modified to engineer robust materials with pre-selected mechanical properties and resorption rates that can be dictated by the intended clinical use. Disulfide-crosslinked HA films were prepared by air oxidation of thiol-modified HA, followed by treatment with 0.3% hydrogen peroxide. The degradation of the disulfide-crosslinked films in vitro was very slow (<10% in 7 days) in buffer alone and shorter (t1/2=3-5 days) in the presence of hyaluronidase (HAse). The cytocompatibility of the disulfide-crosslinked HA films was determined using two separate conditions: (i) in vitro culture of mouse fibroblasts in indirect contract with the films, and (ii) in vitro culture of fibroblasts directly on films coated with poly d-lysine. Excellent cytocompatibility was observed in murine fibroblasts that were cultured in indirect contact with thiolated HA films. Although cells were unable to attach and spread on thiolated HA films, pre-coating the thiolated HA films with poly D-lysine resulted in attachment and spreading equivalent to that observed on polystyrene. Rates of resorption in vivo were obtained by subcutaneous implantation of disulfide-crosslinked HA films into the backs of Wistar rats. Biocompatibility in vivo was determined in both subcutaneous flank and peritoneal cavity implantation of the films in Wistar rats. The disulfide-crosslinked HA films were less than 30% resorbed after 42 days in vivo, and histochemical and cytochemical analysis indicated that the films were well-tolerated with mild inflammatory response at both sites of implantation.

Absorbable Implants↗
PubMed2005

Fabrication of tubular tissue constructs by centrifugal casting of cells suspended in an in situ crosslinkable hyaluronan-gelatin hydrogel.

Achieving the optimal cell density and desired cell distribution in scaffolds is a major goal of cell seeding technologies in tissue engineering. In order to reach this goal, a novel centrifugal casting technology was developed using in situ crosslinkable hyaluronan-based (HA) synthetic extracellular matrix (sECM). Living cells were suspended in a viscous solution of thiol-modified HA and thiol-modified gelatin, a polyethyleneglycol diacrylate crosslinker was added, and a hydrogel was formed during rotation. The tubular tissue constructs consisting of a densely packed cell layer were fabricated with the rotation device operating at 2000 rpm for 10 min. The majority of cells suspended in the HA mixture before rotation were located inside the layer after centrifugal casting. Cells survived the effect of the centrifugal forces experienced under the rotational regime employed. The volume cell density (65.6%) approached the maximal possible volume density based on theoretical sphere packing models. Thus, centrifugal casting allows the fabrication of tubular constructs with the desired redistribution, composition and thickness of cell layers that makes the maximum efficient use of available cells. Centrifugal casting in this sECM would enable rapid fabrication of tissue-engineered vascular grafts, as well as other tubular and planar tissue-engineered constructs.

Animals↗