Collagen Graft Research Articles

Safety and Wound Outcomes Following Genetically Corrected Autologous Epidermal Grafts in Patients With Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a devastating, often fatal, inherited blistering disorder caused by mutations in the COL7A1 gene encoding type VII collagen. Support and palliation are the only current therapies. To evaluate the safety and wound outcomes following genetically corrected autologous epidermal grafts in patients with RDEB. Single-center phase 1 clinical trial conducted in the United States of 4 patients with severe RDEB with a measured area of wounds suitable for grafting of at least 100 cm2. Patients with undetectable type VII collagen keratinocyte expression were excluded. Autologous keratinocytes isolated from biopsy samples collected from 4 patients with RDEB were transduced with good manufacturing practice-grade retrovirus carrying full-length human COL7A1 and assembled into epidermal sheet grafts. Type VII collagen gene-corrected grafts (approximately 35 cm2) were transplanted onto 6 wounds in each of the patients (n = 24 grafts). The primary safety outcomes were recombination competent retrovirus, cancer, and autoimmune reaction. Molecular correction was assessed as type VII collagen expression measured by immunofluorescence and immunoelectron microscopy. Wound healing was assessed using serial photographs taken at 3, 6, and 12 months after grafting. The 4 patients (mean age, 23 years [range, 18-32 years]) were all male with an estimated body surface area affected with RDEB of 4% to 30%. All 24 grafts were well tolerated without serious adverse events. Type VII collagen expression at the dermal-epidermal junction was demonstrated on the graft sites by immunofluorescence microscopy in 9 of 10 biopsy samples (90%) at 3 months, in 8 of 12 samples (66%) at 6 months, and in 5 of 12 samples (42%) at 12 months, including correct type VII collagen localization to anchoring fibrils. Wounds with recombinant type VII collagen graft sites displayed 75% or greater healing at 3 months (21 intact graft sites of 24 wound sites; 87%), 6 months (16/24; 67%), and 12 months (12/24; 50%) compared with baseline wound sites. In this preliminary study of 4 patients with RDEB, there was wound healing in some type VII collagen gene-corrected grafts, but the response was variable among patients and among grafted sites and generally declined over 1 year. Long-term follow-up is necessary for these patients, and controlled trials are needed with a broader range of patients to better understand the potential long-term efficacy of genetically corrected autologous epidermal grafts. clinicaltrials.gov Identifier: NCT01263379.

Grafting collagen on poly (lactic acid) by a simple route to produce electrospun scaffolds, and their cell adhesion evaluation.

Increasing bioactivity and mechanical properties of polymers to produce more suitable scaffold for tissue engineering is a recurrent goal in the development of new biomedical materials. In this study, collagen-functionalized poly (lactic acid), PLA, was obtained by means of a simple grafting route, and electrospun scaffolds were produced to grow cells in vitro; their bioactivity was compared with scaffolds made of physical blends of PLA and collagen. Grafting was verified via nuclear magnetic resonance, attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy. The cell adhesion performance of the scaffolds was studied using macrophages. Elastic modulus (74.7 megapascals) and tensile strength (3.0 megapascals) of the scaffold made from PLA grafted with collagen were substantially higher than the scaffolds made from physical blends of collagen and PLA: 32 and 2.16 megapascals, respectively, implying a more resistant material because of the chemical bond of the polypeptide to PLA. Besides, the fibers had more uniform diameter without defects. Scaffolds made from PLA grafted with collagen presented four-fold increase in cell adhesion than those of PLA blended with collagen. Furthermore, cell spreading within the scaffolds occurred only when collagen-functionalized poly (lactic acid) was used. These results open a new option for the easy tailoring of nanofiber-based scaffolds in three dimensions for tissue engineering.

Complex abdominal wall repair using a combination of porcine dermal matrix and omentum flap in patient with digestive tract fistula: report of a case and review of the literature

Purpose: The purpose of this article is to propose an effective approach for giant abdominal wall defects repair in a contaminated field, using a combination of porcine dermal collagen graft (Permacol) and omental interpositional flap. Case: We report a case of a 41-year-old woman submitted to emergency laparotomy, splenectomy and hepatic haemostasis for massive hemoperitoneum. She developed enteric fistula, cutaneous, muscolar and fascial necrosis leading to evisceration. At the fourth intervention we finally reconstructed abdominal wall defect using a combination of Parmacol and omental flap. Conclusion: The reconstruction of large, full-thickness, eventually contaminated abdominal wall defects is often a challenging undertaking. Similar difficulties are usually encountered with early abdominal wall closure after damage-control surgery and/or open-abdomen management. In these situations the use of synthetic mesh is contrindicated; adsorbable mesh can be used as temporary solution and some techniques of autologous tissue repair have been suggested. Therefore no ideal operative repair technique or prosthetic material for reconstruction of the fascial defect is currently available in the literature. Recently, the development of biologic meshes has shown successful rates in the management of these parietal wall defects. Also in this patient, porcine dermal collagen mesh combined with omental flap allowed us to reconstruct large abdominal wall defect.

Ridge preservation of extraction sockets with chronic pathology using Bio-Oss® Collagen with or without collagen membrane: an experimental study in dogs.

This study aimed to evaluate the dynamics of newly bone formation and dimensional change in diseased extraction sockets using Bio-Oss® Collagen with or without a collagen membrane. In six beagle dogs, right and left 3rd and 4th mandibular premolars were hemisected and the distal roots were removed. Combined endodontic-periodontic lesions were induced in all sites using black silk, collagen sponge, endodontic files, and application of Porphyromonas gingivalis. After 4months, among 4 premolars, three teeth were randomly selected per dog and allocated to the following experimental groups: Control group (no treatment but debridement), Test 1 group (only Bio-Oss® Collagen graft), and Test 2 group (Bio-Oss® Collagen graft with a collagen membrane). After 7months from the baseline, the beagle dogs were sacrificed for histomorphometric and Micro-CT analysis. The vertical distance between buccal and lingual crests in the Control group (2.22±0.26mm) and Test 2 group (1.80±0.16mm) was significantly different. The socket of the Test 2 group (27.04±5.25%) was occupied by a greater quantity of bone graft compared to the Test 1 group (18.49±2.11%). Ridge preservation in diseased extraction sockets could compensate for buccal bone resorption by contact osteogenesis surrounding the bone graft particles at the bucco-coronal area during socket healing, and the application of a collagen membrane at the entrance of the socket is useful for preserving graft material at the coronal part of the socket.

Study on bone regeneration with two different ratios of nano-hydroxyapatite and collagen grafts after tooth extraction in dogs

To compare the effect of bone regeneration with two different ratios of nano-hydroxyapatite(nHA)/collagen(Col) (nHAC) after tooth extraction in canine. Two kinds of nHAC grafts were prepared with different nHA/collagen ratio of 3∶7 and 5∶5. Eighteen male healthy adult dogs had been randomly divided into three groups. Immediately after extraction of the mandibular second premolars, each kind of nHAC was implanted into extraction sockets as follow: Group A, nHA/Col=3∶7(12 sites); Group B, nHA/Col=5∶5(12 sites); Group C, blank control group(12 sites). The bone repairing abilities of the two grafts such as vertical distance of alveolar, CT values, general observation, histological observation, trabecular volume fraction and porosity were separately analyzed at 1st, 3rd and 6th month, respectively (each group had 4 sites in different time periods). nHAC were absorbed gradually after they were implanted into alveolar bone defect and were replaced by new bone. The vertical distance of alveolar bone in Group A([15.76±0.28] mm) was significant higher than that in Group B([14.88±0.36] mm), and CT values of Group A([879±31] HU) were higher than those in Group B([718±29] HU) (P<0.05). The trabecular bone volume percentage of Group A([22.2±0.4]%) was higher than that in Group B([20.3±0.4]%), and the bone porosity of Group A([23.6±0.9]%) was lower than that in Group B([27.6±0.6]%) (P<0.05). In addition, the vertical distance, CT values and the trabecular bone volume percentage of Group C was lower than those in Group A and B, but the bone porosity of Group C was higher. The nHAC with nHA/collagen ratio of 3∶7 could better promote bone regeneration than nHAC with the nHA/collagen ratio of 5∶5 did.

Effects of Collagen Grafting on Cell Behaviors in BCP Scaffold with Interconnected Pore Structure

BackgroundThis study was to investigate the effect of collagen grafted porous biphasic calcium phosphate (BCP) on cell attachment, proliferation, and differentiation. Porous BCP scaffolds with interconnected micropore structure were prepared with were prepared and then grafted with a collagen type I. The hydroxyapatite (HA) and β-tricalcium phosphate (TCP) ratio of the TCP scaffolds was about 60/40 and the collagen was crosslinked on the TCP scaffold surface (collagen-TCP).ResultsThe sintered BCP scaffolds showed fully interconnected micropore structures with submicron-sized grains. The collagen crosslinking in the scaffolds was conducted using the the N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide (NHS) crosslinking method. The cell proliferation of collagen-BCP scaffolds showed a similar result to that of the BCP scaffolds. However, osteoblastic differentiation and cell attachment increased in the collagen-BCP scaffolds.ConclusionsCollagen-BCP scaffold improved the cell attachment ability in early phase and osteoblastic differentiation.

Collagen density gradient on poly(epsilon-caprolactone) surface for the design of 3D printed osteochondral

Event Abstract Back to Event Collagen density gradient on poly(epsilon-caprolactone) surface for the design of 3D printed osteochondral Ugo D'Amora1, Matteo D'Este2, David Eglin2, Antonio Gloria1, Roberto De Santis1, Mauro Alini2 and Luigi Ambrosio1, 3 1 National Research Council of Italy, Institute of Polymers, Composites and Biomaterials, Italy 2 AO Research Institute Davos, Switzerland 3 National Research Council of Italy, Chemical Science & Materials Technology Department, Italy Introduction: The ability to engineer scaffolds which resemble the transition between tissues, like cartilage and bone, has yet to be achieved. Indeed, such constructs should present several continuous gradients in terms of geometry, stiffness and biochemical composition to mimic tissue organization. Although the introduction of fused deposition modeling (FDM) techniques allows tailoring of mechanical, mass transport and morphological properties, the possibility to additionally functionalize such structures by introducing biochemical signal gradients has not been fully explored. Thus, a two-step functionalization method in which collagen was covalently grafted to a polyester surface is presented. A continuous collagen gradient was created along the length of a polymer surface which was characterized for collagen content, topography and cell adhesion. Materials and Methods: Poly(ε-caprolactone) (PCL) surfaces were produced by a melting/molding technique. First, the PCL surfaces were modified by immersing the substrates in a 1,6-hexanediamine/isopropanol solution. An amino-group (NH2) density gradient was achieved along the length of the substrate via the controlled surface exposure into the reactive solution[1]. In the second step, lyophilized collagen type I was grafted using a carbodiimide reaction. Ninhydrin and hydroxyproline assays, contact angle measurements, confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FTIR), fast green and picrosirius red staining were performed to characterize the surfaces and gradients. Results and Discussion: The NH2 concentration varied between 5*10-7 mol/cm2 (15 min processing) and 15*10-7 mol/cm2 (45 min processing). (Fig. 1). Figure 1. NH2 concentration as function of the reaction times and of the position along the PCL surface. The PCL-NH2 substrates were treated with Rhodamine B Isothiocyanate to visualize the gradient by using CLSM. The fluorescence intensity decreased from 80 (a.u.) for the region treated for 45 minutes to 10 (a.u.) for the PCL zone. The region treated for 45 minutes showed a greater roughness, probably due to surface erosion of the material. (Fig. 2). Figure 2. Representative images of PCL-NH2-Rhod surfaces functionalized after right) 45; middle) 30; and left) 15 minutes of treatment. Static water contact angle decreased by about 15° whilst collagen density increased with increased NH2 concentration. The introduction of collagen improved the hydrophilicity of the surfaces. Microscopy imaging/analysis visualized the collagen distribution onto the substrates whilst FTIR confirmed collagen grafting and preservation of its helical structure. Conclusion: A two-step functionalization procedure protein was developed. A continuous collagen gradient along the length of a PCL substrate was confirmed by morphological and physico-chemical analysis. Future studies will apply the methodology to FDM PCL-based scaffolds for the repair/regeneration of focal osteochondral defects. The authors would like to thank FIRB MERIT project (GAE: P0000570) for providing financial support

Comparison of bone regeneration in alveolar bone of dogs on mineralized collagen grafts with two composition ratios of nano-hydroxyapatite and collagen

To study the effect of two composition ratios of nano-hydroxyapatite and collagen (NHAC) composites on repairing alveolar bone defect of dogs. Eighteen healthy adult dogs were randomly divided into three groups. Two kinds of the NHAC composites were prepared according to the constituent ratios of 3:7 and 5:5; immediately after extraction of the mandibular second premolars, each kind of the NHAC composite was implanted into extraction socket, respectively: Group I, nHA/Col = 3:7; Group II, nHA/Col = 5:5 and Group III, blank control group. The bone-repairing ability of the two grafts was separately analyzed by morphometric measurement, X-ray tomography examination and biomechanical analysis at 1st, 3rd and 6th month post-surgical, respectively.The NHAC composites were absorbed gradually after implanting into alveolar bone defect and were replaced by new bone. The ratios of new bone formation of Group I was significantly higher than that of Group II after 3 months (P < 0.05). The structure and bioactive performance can be improved when the ratio between the collagen and the hydroxyapatite was reasonable, and the repairing ability and effect in extraction sockets are obviously better.

New technique: AlloDerm® interposition arthroplasty of thumb carpo-metacarpal joint

Excision arthroplasty is an alternative procedure for degenerative arthritis of the trapezium carpal bone that has failed non-surgical treatment. Autologous or heterologous interposition materials are used following excision of the trapezium, but may not prevent first metacarpal-scaphoid joint collapse or subsidence. AlloDerm® is a cadaver-harvested, immunologically inert dermal collagen graft. This report documents the uncomplicated use of AlloDerm® in 13 thumbs of 9 patients who had first carpometacarpal (CMC) joint excision interposition arthroplasty for degenerative arthritis. Joints functioned well after arthroplasty with AlloDerm®. These clinical results compare favorably to results in 6 Silicon implant CMC arthroplasty patients, and 3 autologous dermal graft CMC arthroplasty patients. Future clinical research, on joint stability, the durability of this collagen graft, newer dermal collagen substrates, and prevention of metacarpal subsidence, will determine the ultimate role of AlloDerm® in interposition arthroplasty.

Comparison of Collagen Graft Fixation Methods in the Porcine Knee: Implications for Matrix-Assisted Chondrocyte Implantation and Second-Generation Autologous Chondrocyte Implantation

To evaluate the fixation integrity at time zero of a type I/III collagen patch secured to a chondral defect in the porcine knee using methods typically employed in autologous chondrocyte implantation (ACI) and matrix-assisted chondrocyte implantation. Twenty-four porcine knee specimens underwent a medial parapatellar arthrotomy. A prefabricated template was used to create cartilage defects of 2 cm(2) in the medial femoral condyle. A size-matched collagen patch was fashioned. Four methods of fixation to the chondral defect were analyzed: group 1-saline, group 2-fibrin glue around the periphery of the patch, group 3-fibrin glue applied to the base of the defect and around the periphery of the patch, group 4-6-0 vicryl suture and fibrin glue around the periphery of the patch. Collagen patch fixation was assessed at intervals of 60, 300, 600, 900, and 1,200 cycles from full extension to 90° of flexion, performed manually without application of axial force. Patch fixation was evaluated by 2 independent observers using a customized scoring scale. Mean peripheral detachment of the patch and chondral defect uncovering remained less than 25% for all groups. Area of defect uncovering was significantly increased in group 2 compared with group 4 after 900 and 1,200 cycles (P= .0014 and P= .0025, respectively). Fibrin glue applied to the base of the defect, or suturing of the patch, reduced deformation significantly after 900 cycles. Suture increases the stability of fixation of a type I/III collagen patch to a chondral defect better than fibrin glue alone in the porcine knee after repetitive cycling, with respect to patch detachment and chondral defect uncovering. Application of fibrin glue to the base of the defect, or securing the patch with suture, decreases collagen patch deformation. In cases where minimally invasive techniques do not allow suture fixation of the collagen patch, scaffold fixation may be compromised during articular motion protocols typically used after second- and third-generation ACI procedures.

Double-layered collagen graft to the radial forearm free flap donor sites without skin graft.

BackgroundRadial forearm free flap is the most reliable flap for intraoral soft tissue reconstruction after cancer ablation surgery. However, unesthetic scar of the donor site and the need for a second donor site for skin graft are major disadvantages of the forearm flap. The purpose of this study was to report the clinical results of double-layered collagen graft to the donor site of the forearm free flap without skin graft.MethodsTwenty-two consecutive patients who underwent oral cancer ablation and forearm reconstruction between April 2010 and November 2013 were included in this study. Male to female ratio was 12:10, and average age was 61.0 years old (27–84). Double-layered collagen was grafted to the donor site of the forearm free flap and healed for secondary intention. Upper silicone had been trimmed at the periphery during secondary intention, and dry dressing was used. Postoperative scar healing and esthetic results and function were evaluated.ResultsAn average follow-up period was 34.9 months. The scar area was decreased to 63.9 % in average. The complete healing was obtained between 1.5 and 3 months according to the defect size. There was no functional defect or impairment 3 months after operation. All patients were satisfied with the esthetic results. Three patients died of recurred cancer.ConclusionsDouble-layered collagen graft was successfully performed in this study. Without the thigh skin graft, patients had experienced less painful postoperative healing periods and discomfort.

Use of a porcine urinary bladder acellular matrix for corneal reconstruction in dogs and cats.

To describe the use of a porcine urinary bladder acellular matrix for surgical reconstruction of the cornea in cases of canine and feline deep corneal ulcers, and feline corneal sequestra. Twenty-seven dogs and three cats with deep corneal ulcers and seven cats with corneal sequestra were included in the study with overall 38 eyes. For each patient, the necrotic material (ie corneal sequestrum or collagenolytic tissue) was removed by circular lamellar keratectomy. The collagen graft was then cut and prepared to match the stromal defect and then sutured into the lamellar keratectomy bed using interrupted and continuous patterns of absorbable polyglactin 9-0 sutures. Postoperative medical treatment consisted of topical and systemic administration of antibiotics, combined with topical administration of atropine sulfate. The animals were examined 18, 45, and 90 days after the surgery. Postoperative examination revealed complete integration of the biomaterial in 93.5% of ulceration cases in both species and in 100% of feline corneal sequestrum cases. In two cases of ulceration (1 dog and 1 cat), progression of the collagenolytic process at the graft periphery required an additional conjunctival graft 7 days after the first surgery. At 90 days post-op, 100% of the eyes were sighted. Use of a porcine urinary bladder acellular matrix appears to be effective in the surgical management of deep corneal ulcers and feline corneal sequestra.

Clinical evaluation following the use of mineralized collagen graft for bone defects in revision total hip arthroplasty

Revision total hip arthroplasty (THA) with massive bone loss has been a real challenge for orthopaedic surgeons. Here we describe an approach using mineralized collagen (MC) graft to reconstruct acetabulum and femur with massive bone defects. We identified 89 patients suffering acetabular or femoral bone defects after primary THA, who required revision THA for this study. During the surgery, MC was applied to reconstruct both the acetabular and femoral defects. Harris hip score was used to evaluate hip function while radiographs were taken to estimate bone formation in the defect regions. The average follow-up period was 33.6 ± 2.4 months. None of the components needed re-revised. Mean Harris hip scores were 42.5 ± 3.5 before operation, 75.2 ± 4.0 at 10th month and 95.0 ± 3.6 at the final follow-up. There were no instances of deep infection, severe venous thrombosis or nerve palsy. The present study demonstrated that MC graft can serve as a promising option for revision THA with massive bone deficiency. Meanwhile, extended follow-up is needed to further prove its long-term performance.

Preparation and Surface Sizing Application of Sizing Agent Based on Collagen from Leather Waste

Collagen extracted from leather waste was modified with maleic anhydride. Then, using ammonium persulfate as an initiator, by pre-modifying collagen reacted with styrene and ethyl acrylate monomers, a vinyl-grafted collagen sizing agent (VGCSA) for paper was prepared. Before the experiment, the performance of VGCSA was tested and VGCSA emulsion was applied to the surface sizing of the corrugated paper. Effects of the amount of VGCSA, the compound proportion of VGCSA, and starch and styrene-acrylic emulsion were studied relative to paper properties. The morphological changes of the paper before and after sizing were characterized by SEM. It was found that the collagen reacted with styrene and ethyl acrylate monomers. Through the grafting of vinyl and collagen, the crystallinity and thermal stability of VGCSA increased. The structure of VGCSA was spherical with a uniform size, and the average particle size was approximately 350 to 400 nm. After being sized, the surface fibers of paper became smooth and orderly. The optimal sizing of VGCSA was 8 g/m2. The optimal proportion of VGCSA with starch was 4:6, and the optimal proportion of VGCSA with SAE was 2:8. The research indicates that collagen extracted from leather waste could be used as a biomaterial, and environmental and economic benefits could be created as well.

The significance of grafting collagen on polycaprolactone composite scaffolds: processing-structure-functional property relationship.

The study concerns processing-structure-functional property relationship in organic-inorganic hybrid scaffolds based on grafted collagen for bone tissue engineering. Biodegradable polyester, polycaprolactone (PCL) and nanohydroxyapatite were used to fabricate three-dimensional porous scaffolds by adopting a combination of solvent casting, particulate leaching, and polymer leaching approaches. The PCL scaffold was subsequently surface modified by chemical bonding of 1,6-hexanediamine to the ester groups of PCL to introduce free NH2 groups. The introduction of NH2 groups as active sites enabled immobilization of biocompatible macromolecule, collagen, on the aminolyzed PCL via a cross-linking agent, glutaraldehyde. The osteoblasts' functions, notably cell adhesion, proliferation, and mineralization, were favorably modulated because of the chemical interaction between Arg-Gly-Asp domains in collagen molecule and integrin receptor in the cell membrane. The study underscores the significance of grafting collagen on PCL-nHA scaffold in modulating cellular activity and biological functions expanding its current use in soft tissue engineering to hard tissue regeneration.

Use of Platelet-Rich Plasma for Collagen Matrixes Revitalization with Human Fibroblast

We studied in vitro attachment, proliferation and survival of сadaver skin fibroblasts in collagen bands, dermal matrix and cancellous demineralized bone, enriched with platelet components. It was shown, that PRP enhanced revitalization of collagen grafts, especially followed by components of activated or freezed platelets. Fibroblasts had the best rate of proliferative activity in response to 150 pg platelet derived growth factor (PDGF), released from 100 million platelets with granules and measured for 100 × 103 cultivated cells. The use of platelet-derived material could increase fibroblast proliferation activity for 1.5-3 times in all types of collagen transplants without damage or decay of cell’s biological value.

Clinical Observations on Repair of Non-Infected Bone Nonunion by Using Mineralized Collagen Graft

Clinical Observations on Repair of Non-Infected Bone Nonunion by Using Mineralized Collagen Graft Jian-Ming Kou1 ∗, Ting-You Fu2, Xue-Jun Jia1, Jian-Wen Hou1, Chong Gao1, Yuan-Zheng Ma3, Zhi-Ye Qiu4, and Fu-Zhai Cui4 1Department of Orthopedics, The Second People’s Hospital of Lianyungang, Lianyungang 222000, China 2Department of Orthopedic Surgery, The 401th Hospital of Chinese People’s Liberation Army, Qingdao 266100, China 3Department of Orthopedics, The 309th Hospital of Chinese People’s Liberation Army, Beijing 100091, China 4Institute for Regenerative Medicine and Biomimetic Materials, Tsinghua University, Beijing 100084, China

Evaluation of porcine xenograft in collateral ligament reconstruction in beagle dogs

This study evaluated the effectiveness of irradiated porcine tendon xenografts for lateral collateral ligament (LCL) reconstruction. Twenty healthy adult beagle dogs underwent LCL reconstruction using irradiated porcine tendons treated with poly-gamma-glutamic acid. Serological and histological assessments were performed to evaluate host immunological response at 3 and 12 months after surgery. The healing and functional integrity of the LCL reconstructions were assessed by mechanical testing and gait analysis. Histological assessment of the porcine xenografts showed gradual host cellular infiltration and graft collagen remodeling during the healing process. Porcine xenografts showed angiogenesis and no signs of inflammatory reaction. Additionally, biomechanical and gait evaluations supported graft functional integration with no differences between normal and porcine xenograft reconstruction at 12 months after surgery. Irradiated porcine xenografts showed greater cellular responses and healing properties in short- and long-term evaluations. Irradiated porcine tendons appear to be useful as xenografts for the reconstruction of damaged ligaments.

Esthetic and functional surgery and reconstruction after oral cancer ablation

Oral cancer ablation surgery results in tissue defects with functional loss. Accompanying neck dissection results in facial nerve weakness and dysmorphic changes. To minimize the complications after oral cancer surgery, accurate dissection without damaging facial nerve and vital structures are mandatory. Marginal mandibular branch of facial nerve should be dissected or contained in the superficial layer of deep cervical fascia to minimized facial palsy after operation. Reconstruction after cancer ablations is routine procedures and free flap reconstruction is the most commonly used. Radial forearm free flap is the most versatile flap to reconstruct soft tissue defects and it is easy to design according to the defect size and shape. However, donor site scar and secondary skin graft from thigh result in unesthetic and cumbersome wounds. Double layered collagen graft in the donor site could reduce secondary donor site for skin graft. In conclusion, oral and maxillofacial surgeon should know the exact anatomy of the face and neck during neck dissection. Radial forearm free flap is most versatile flap for soft tissue reconstruction and double collagen graft can reduce postoperative scar and there is no need for secondary skin graft.

Biomimetic modified clinical-grade POSS-PCU nanocomposite polymer for bypass graft applications: a preliminary assessment of endothelial cell adhesion and haemocompatibility.

To date, there are no small internal diameter (<5mm) vascular grafts that are FDA approved for clinical use due to high failure rates from thrombosis and unwanted cell proliferation. The ideal conditions to enhance bioengineered grafts would be the blood contacting lumen of the bypass graft fully covered by endothelial cells (ECs). As a strategy towards this aim, we hypothesized that by immobilising biomolecules on the surface of the polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane (POSS-PCU) nanocomposite polymers, which contain binding sites and ligands for cell surface receptors similar to extracellular matrix (ECM) will positively influence the attachment and proliferation of ECs. Since, the surface of POSS-PCU is inert and not directly suitable for immobilisation of biomolecules, plasma graft polymerisation is a suitable method to modify the surface properties ready for immobilisation and biofunctionalisation. POSS-PCU was activated by plasma treatment in air/O2 to from hydroperoxides (-OH, -OOH), and then carboxylated via plasma polymerisation of a 30% acrylic acid solution (Poly-AA) using a two-step plasma treatment (TSPT) process. Collagen type I, a major component of ECM, was covalently immobilised to mimic the ECM structures to ECs (5mg/ml) using a two-step chemical reaction using EDC chemistry. Successful immobilisation of poly-AA and collagen on to the nanocomposites was confirmed using Toluidine Blue staining and the Bradford assay. Un-treated POSS-PCU served as a simple control. The impact of collagen grafting on the physical, mechanical and biological properties of POSS-PCU was evaluated via contact angle (θ) measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA), ECs adhesion and proliferation followed by platelet adhesion and haemolysis ratio (HR) tests. Poly-AA content on each of the plasma treated nanocomposite films increased on Low, Med and High samples due to more carboxylic acid (-COOH) groups at the surface forming amide (-NH2) bonds. The amount of -COOH groups on each of the Low, Med and High nanocomposites correlated with Poly-AA grafting density at 14.7±0.9, 18.9±0.9, and 34.2±2.4 μg/cm(2). Immobilisation of collagen type I on to nanocomposite surface was also found to increase significantly on the Low, Med and High samples from 22±4, 150±15, and 219±17 μg/cm(2), respectively. The level of ECs and their adhesion efficiency were improved with increasing amounts of grafted collagen I. The maximum adhesion of ECs was found on the highest collagen type I coated nanocomposites. Platelet adhesion and activation also increased with increasing collagen density. The obtained HR values for all of the treated samples were well within the acceptable standards for biomaterials (<5% HR). Poly-AA-g-POSS-PCU surfaces offer binding sites for the covalent bonding of collagen type I and other biomolecules such as fibronectin by exposure of RGD cell binding domains and growth factors using EDC cross-linking chemistry. Collagen type I modification can yield accelerated EC growth and enhance the endothelialisation of POSS-PCU nanocomposites, and the amount of immobilised collagen can control the level of platelet adhesion on functionalized POSS-PCU via TSPT and poly acrylic acid (poly-AA) treatment. Such surface modification procedures of polymeric surfaces can improve the patency rate of POSS-PCU nanocomposites as vascular bypass grafts in the preparation of a range of medical devices ready for pre-clinical and in vivo evaluation.