Duraplasty with biosynthetic cellulose: an experimental study

Fabrication strategies and biomedical applications of three-dimensional bacterial cellulose-based scaffolds: A review

Bacterial cellulose (BC), an extracellular polysaccharide, is a versatile biopolymer due to its intrinsic physicochemical properties, broad-spectrum applications, and remarkable achievements in different fields, especially in the biomedical field. Presently, the focus of BC-related research is on the development of scaffolds containing other materials for in-vitro and in-vivo biomedical applications. To this end, prime research objectives concern the biocompatibility of BC and the development of three-dimensional (3D) BC-based scaffolds. This review summarizes the techniques used to develop 3D BC scaffolds and discusses their potential merits and limitations. In addition, we discuss the various biomedical applications of BC-based scaffolds for which the 3D BC matrix confers desired structural and conformational features. Overall, this review provides comprehensive coverage of the idea, requirements, synthetic strategies, and current and prospective applications of 3D BC scaffolds, and thus, should be useful for researchers working with polysaccharides, biopolymers, or composite materials.

Biomechanical characterization of human temporal muscle fascia in uniaxial tensile tests for graft purposes in duraplasty

The human temporal muscle fascia (TMF) is used frequently as a graft material for duraplasty. Encompassing biomechanical analyses of TMF are lacking, impeding a well-grounded biomechanical comparison of the TMF to other graft materials used for duraplasty, including the dura mater itself. In this study, we investigated the biomechanical properties of 74 human TMF samples in comparison to an age-matched group of dura mater samples. The TMF showed an elastic modulus of 36 ± 19 MPa, an ultimate tensile strength of 3.6 ± 1.7 MPa, a maximum force of 16 ± 8 N, a maximum strain of 13 ± 4% and a strain at failure of 17 ± 6%. Post-mortem interval correlated weakly with elastic modulus (r = 0.255, p = 0.048) and the strain at failure (r =  − 0.306, p = 0.022) for TMF. The age of the donors did not reveal significant correlations to the TMF mechanical parameters. Compared to the dura mater, the here investigated TMF showed a significantly lower elastic modulus and ultimate tensile strength, but a larger strain at failure. The human TMF with a post-mortem interval of up to 146 h may be considered a mechanically suitable graft material for duraplasty when stored at a temperature of 4 °C.

Biomimetic nanofibrous hybrid hydrogel membranes with sustained growth factor release for guided bone regeneration

A biomimetic nanofibrous membrane can immobilize growth factors or agents to obtain sustained release and prolonged effect in tissue engineering.

Bacterial Nanocellulose in Dentistry: Perspectives and Challenges

Bacterial cellulose (BC) is a natural polymer that has fascinating attributes, such as biocompatibility, low cost, and ease of processing, being considered a very interesting biomaterial due to its options for moldability and combination. Thus, BC-based compounds (for example, BC/collagen, BC/gelatin, BC/fibroin, BC/chitosan, etc.) have improved properties and/or functionality, allowing for various biomedical applications, such as artificial blood vessels and microvessels, artificial skin, and wounds dressing among others. Despite the wide applicability in biomedicine and tissue engineering, there is a lack of updated scientific reports on applications related to dentistry, since BC has great potential for this. It has been used mainly in the regeneration of periodontal tissue, surgical dressings, intraoral wounds, and also in the regeneration of pulp tissue. This review describes the properties and advantages of some BC studies focused on dental and oral applications, including the design of implants, scaffolds, and wound-dressing materials, as well as carriers for drug delivery in dentistry. Aligned to the current trends and biotechnology evolutions, BC-based nanocomposites offer a great field to be explored and other novel features can be expected in relation to oral and bone tissue repair in the near future.

In vivo evaluation of bilayer ORC/PCL composites in a rabbit model for using as a dural substitute

OBJECTIVE

After a neurosurgical procedure, dural closure is commonly needed to prevent cerebrospinal fluids (CSF) leakage and to reduce the risk of complications, including infections and chronic inflammatory reactions. Although several dural substitutes have been developed, their manufacturing processes are complicated and costly and that many of them have been implicated in causing postoperative complications. This study aimed to assess the effectiveness and safety of new bilayer ORC/PCL composites in a rabbit model.

METHODS

Two formulations of bilayer oxidized regenerated cellulose (ORC)/poly ε-caprolactone (PCL) knitted fabric-reinforced composites and an autologous graft (pericranium) were employed for dural closure in forty-five male rabbits. Systemic reaction and the local reaction of the samples were assessed and compared at one-, three- and six-months post-implantation by blood chemistry and gross, and microscopic assessment using hematoxylin-eosin and Masson's trichrome stains.

RESULTS

No signs of CSF leakage or systemic infection were seen for all samples. All samples demonstrated minimal adhesion to adjacent tissues. The degree of host fibrous connective tissue ingrowth into both composites was comparable to that of the autologous group, but bone formation and osteoclast activities were significantly greater. Both composites progressively degraded over times and the residual thickness of the nonporous layer was 50% of the initial thickness at six months post-implantation.

DISCUSSION

Bilayer ORC/PCL composites were successfully employed for dural closure in the rabbit model. They were biocompatible and could support dural regeneration comparable to that of the autologous group, but induced greater osteogenesis.

Traumatic perforations of the tympanic membrane: immediate clinical recovery with the use of bacterial cellulose film

Introduction

Perforation of the tympanic membrane is a reasonably frequent diagnosis in otorhinolaryngologists’ offices. The expectant management is to wait for spontaneous healing, which usually occurs in almost all cases in a few weeks. However, while waiting for healing to be completed, the patients may experience uncomfortable symptoms. Although some research suggests the use of various materials to aid in the recovery of the tympanic membrane, none presented robust evidence of improvement in the cicatricial process. Nevertheless, the occlusion of the perforation with some material of specific texture and resistance can alleviate the patients’ symptoms and accelerate the healing process.

Objective

To evaluate the clinical (symptomatic and functional) improvement after the placement of bacterial cellulose film (Bionext®) on tympanic membrane perforations (traumatic).

Methods

We evaluated 24 patients, victims of traumatic perforations of the tympanic membrane, who were evaluated in the Otorhinolaryngology Emergency Room. Following otoscopy and audiometric examination was performed, before and after the use of cellulose film occluding the tympanic membrane perforation.

Results

Twenty-four patients were included, whose degree of overall discomfort caused by the tympanic membrane perforation and the presence of symptoms of autophonia, ear fullness and tinnitus were investigated. The mean score attributed to the overall annoyance caused by tympanic membrane perforation was 7.79, decreasing to a mean value of 2.25 after the film application. Symptom evaluation also showed improvement after using the film: autophonia decreased from a mean value of 6.25 to 2.08, tinnitus from 7 to 1.92 and ear fullness from 7.29 to 1.96. The auditory analysis showed mean threshold values still within the normal range at low and medium frequencies, with slight hearing loss at acute frequencies, but with significant improvement at all frequencies, with the exception of 8000 Hz, after film use.

Conclusion

The use of bacterial cellulose film fragment on traumatic perforations of the tympanic membrane promoted immediate functional and symptomatic recovery in the assessed patients.

Preparation and Characterization of Resorbable Bacterial Cellulose Membranes Treated by Electron Beam Irradiation for Guided Bone Regeneration

Bacterial cellulose (BC) is an excellent biomaterial with many medical applications. In this study, resorbable BC membranes were prepared for guided bone regeneration (GBR) using an irradiation technique for applications in the dental field. Electron beam irradiation (EI) increases biodegradation by severing the glucose bonds of BC. BC membranes irradiated at 100 kGy or 300 kGy were used to determine optimal electron beam doses. Electron beam irradiated BC membranes (EI-BCMs) were evaluated by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, thermal gravimetric analysis (TGA), and using wet tensile strength measurements. In addition, in vitro cell studies were conducted in order to confirm the cytocompatibility of EI-BCMs. Cell viabilities of NIH3T3 cells on 100k and 300k EI-BCMs (100 kGy and 300 kGy irradiated BC membranes) were significantly greater than on NI-BCMs after 3 and 7 days (p < 0.05). Bone regeneration by EI-BCMs and their biodegradabilities were also evaluated using in vivo rat calvarial defect models for 4 and 8 weeks. Histometric results showed 100k EI-BCMs exhibited significantly larger new bone area (NBA; %) than 300k EI-BCMs at 8 weeks after implantation (p < 0.05). Mechanical, chemical, and biological analyses showed EI-BCMs effectively interacted with cells and promoted bone regeneration.

The Efficacy of Electron Beam Irradiated Bacterial Cellulose Membranes as Compared with Collagen Membranes on Guided Bone Regeneration in Peri-Implant Bone Defects

Bacterial cellulose (BC) is a natural polysaccharide produced by some bacteria, and consists of a linear polymer linked by β-(1,4) glycosidic bonds. BC has been developed as a material for tissue regeneration purposes. This study was conducted to evaluate the efficacy of resorbable electron beam irradiated BC membranes (EI-BCMs) for guided bone regeneration (GBR). The electron beam irradiation (EI) was introduced to control the biodegradability of BC for dental applications. EI-BCMs had higher porosity than collagen membranes (CMs), and had similar wet tensile strengths to CMs. NIH3T3 cell adhesion and proliferation on EI-BCMs were not significantly different from those on CMs (p > 0.05). Micro-computed tomography (μCT) and histometric analysis in peri-implant dehiscence defects of beagle dogs showed that EI-BCMs were non-significantly different from CMs in terms of new bone area (NBA; %), remaining bone substitute volume (RBA; %) and bone-to-implant contact (BIC; %) (p > 0.05). These results suggest resorbable EI-BCMs can be used as an alternative biomaterial for bone tissue regeneration.

Biocompatible bacterial cellulose membrane in dural defect repair of rat

Duraplasty is necessary in nearly 30% of all neurological surgeries. Different tissues and materials have been evaluated in dura mater repair or as dural substitutes in neurosurgery. The aim was to evaluate the biocompatibility of the bacterial cellulose (BC) membranes, produced from sugarcane molasses, for dural defect repair in rats. Forty adults males Wistar rats divided into two groups: a control (ePTFE) and an experimental (BC). Bilateral frontoparietal craniectomy was performed, and a dural defect was created. The arachnoid underlying defect was disrupted with a narrow hook. The animals were observed for 120 days. There were no cases of infection, cerebrospinal fluid fistulae, delayed hemorrhages, behavior disturbances, seizures and palsies. The BC membrane showed to have suitable biocompatibility properties, was not induced immune reaction, nor chronic inflammatory response and absence of neurotoxicity signals.

Experimental evaluation of new chitin-chitosan graft for duraplasty

Natural materials such as collagen and alginate have promising applications as dural graft substitutes. These materials are able to restore the dural defect and create optimal conditions for the development of connective tissue at the site of injury. A promising material for biomedical applications is chitosan-a linear polysaccharide obtained by the deacetylation of chitin. It has been found to be nontoxic, biodegradable, biofunctional and biocompatible in addition to having antimicrobial characteristics. In this study we designed new chitin-chitosan substitutes for dura mater closure and evaluated their effectiveness and safety. Chitosan films were produced from 3 % of chitosan (molar mass-200, 500 or 700 kDa, deacetylation rate 80-90%) with addition of 20% of chitin. Antimicrobial effictively and cell viability were analysed for the different molar masses of chitosan. The film containing chitosan of molar mass 200 kDa, had the best antimicrobial and biological activity and was successfully used for experimental duraplasty in an in vivo model. In conclusion the chitin-chitosan membrane designed here met the requirements for a dura matter graft exhibiting the ability to support cell growth, inhibit microbial growth and biodegradade at an appropriate rate. Therefore this is a promising material for clinical duroplasty.

A multipurpose natural and renewable polymer in medical applications: Bacterial cellulose

Bacterial cellulose (BC) produced by some bacteria, among them Gluconacetobacter xylinum, which secrets an abundant 3D networks fibrils, represents an interesting emerging biocompatible nanomaterial. Since its discovery BC has shown tremendous potential in a wide range of biomedical applications, such as artificial skin, artificial blood vessels and microvessels, wound dressing, among others. BC can be easily manipulated to improve its properties and/or functionalities resulting in several BC based nanocomposites. As example BC/collagen, BC/gelatin, BC/Fibroin, BC/Chitosan, etc. Thus, the aim of this review is to discuss about the applicability in biomedicine by demonstrating a variety of forms of this biopolymer highlighting in detail some qualities of bacterial cellulose. Therefore, various biomedical applications ranging from implants and scaffolds, carriers for drug delivery, wound-dressing materials, etc. that were reported until date will be presented.

Endoscopic surgery for the antenatal treatment of myelomeningocele: the CECAM trial

BACKGROUND

A recent randomized clinical trial named Management of Myelomeningocele Study (MOMS trial) showed that prenatal correction of open spina bifida (OSB) via open fetal surgery was associated with improved infant neurological outcomes relative to postnatal repair, but at the expense of increased maternal morbidity.

OBJECTIVE

We sought to report the final results of our phase I trial (Cirurgia Endoscópica para Correção Antenatal da Meningomielocele [CECAM]) on the feasibility, safety, potential benefits, and side effects of the fetoscopic treatment of OSB using our unique surgical technique.

STUDY DESIGN

Ten consecutive pregnancies with lumbosacral OSB were enrolled in the study. Surgeries were performed percutaneously under general anesthesia with 3 ports and partial carbon dioxide insufflation. After appropriate surgical positioning of the fetus, the neuroplacode was released with scissors and the skin was undermined to place a biocellulose patch over the lesion. The skin was closed over the patch using a single running stitch. Preoperative, postoperative, and postnatal magnetic resonance imaging were performed to assess hindbrain herniation. Neurodevelopmental evaluation was performed before discharge and at 3, 6, and 12 months. All cases were delivered by cesarean delivery, at which time the uterus was assessed for evidence of thinning or dehiscence.

RESULTS

The median gestational age at the time of surgery was 27 weeks (range 25-28 weeks). Endoscopic repair was completed in 8 of 10 fetuses. Two cases were unsuccessful due to loss of uterine access. The mean gestational age at birth was 32.4 weeks with a mean latency of 5.6 weeks between surgery and delivery (range 2-8 weeks). There was 1 fetal and 1 neonatal demise, and 1 unsuccessful case underwent postnatal repair. Of the 7 infants available for analysis, complete reversal of hindbrain herniation occurred in 6 of 7 babies. Three babies required ventriculoperitoneal shunting or third ventriculostomy. Functional motor level was the same or better than the anatomical level in 6 of 7 cases. There was no significant maternal morbidity and no evidence of myometrial thinning or dehiscence. However, surgeries were complicated by premature rupture of membrane and prematurity.

CONCLUSION

Our study suggests that the antenatal treatment of OSB using a fetoscopic approach and our unique surgical technique can result in a watertight seal, reversal of the hindbrain herniation, and better than expected motor function. Our technique differs substantially from the classic repair of OSB used in prior open fetal surgery and fetoscopic studies, in which the dura mater is dissected and the defect is closed in multiple layers. Instead, we use a biocellulose patch placed over the lesion and simple closure of the skin. As such, our technique is an alternative to the current paradigms in the antenatal treatment of OSB. Our clinical outcomes are in line with the results of our extensive prior animal work. Maternal benefits of our approach and technique include minimal morbidity and no myometrial legacy. Current limitations of the approach include potential loss of access, premature rupture of membranes, and attendant prematurity. Phase II trials are needed to prevent these complications and to further assess the risks and benefits of our distinct surgical approach and technique.

The feasibility of using irreversible electroporation to introduce pores in bacterial cellulose scaffolds for tissue engineering

This work investigates the feasibility of the use of irreversible electroporation (IRE) in the biofabrication of 3D cellulose nanofibril networks via the bacterial strain Gluconacetobacter xylinus. IRE uses electrical pulses to increase membrane permeability by altering the transmembrane potential; past a threshold, damage to the cell becomes too great and leads to cell death. We hypothesized that using IRE to kill the bacteria at specific locations and particular times, we could introduce conduits in the overall scaffold by preventing cellulose biosynthesis locally. Through mathematical modeling and experimental techniques, electrical effects were investigated and the parameters for IRE of G. xylinus were determined. We found that for a specific set of parameters, an applied electric field of 8 to 12.5 kV/cm, producing a local field of 3 kV/cm, was sufficient to kill most of the bacteria and create a localized pore. However, an applied electric field of 17.5 kV/cm was required to kill all. Results suggest that IRE may be an effective tool to create scaffolds with appropriate porosity for orthopedic applications. Ideally, these engineered scaffolds could be used to successfully treat osteochondral defects.

Applications of bacterial cellulose and its composites in biomedicine

Bacterial cellulose produced by few but specific microbial genera is an extremely pure natural exopolysaccharide. Besides providing adhesive properties and a competitive advantage to the cellulose over-producer, bacterial cellulose confers UV protection, ensures maintenance of an aerobic environment, retains moisture, protects against heavy metal stress, etc. This unique nanostructured matrix is being widely explored for various medical and nonmedical applications. It can be produced in various shapes and forms because of which it finds varied uses in biomedicine. The attributes of bacterial cellulose such as biocompatibility, haemocompatibility, mechanical strength, microporosity and biodegradability with its unique surface chemistry make it ideally suited for a plethora of biomedical applications. This review highlights these qualities of bacterial cellulose in detail with emphasis on reports that prove its utility in biomedicine. It also gives an in-depth account of various biomedical applications ranging from implants and scaffolds for tissue engineering, carriers for drug delivery, wound-dressing materials, etc. that are reported until date. Besides, perspectives on limitations of commercialisation of bacterial cellulose have been presented. This review is also an update on the variety of low-cost substrates used for production of bacterial cellulose and its nonmedical applications and includes patents and commercial products based on bacterial cellulose.

Comparison between two surgical techniques for prenatal correction of meningomyelocele in sheep

OBJECTIVE: To compare the classical neurosurgical technique with a new simplified technique for prenatal repair of a myelomeningocelelike defect in sheep. METHODS: A myelomeningocele-like defect (laminectomy and dural excision) was created in the lumbar region on day 90 of gestation in 9 pregnant sheep. Correction technique was randomized. In Group 1 the defect was corrected using the classic neurosurgical technique of three-layer suture (dura mater, muscle and skin closure) performed by a neurosurgeon. In Group 2, a fetal medicine specialist used a biosynthetic cellulose patch to protect the spinal cord and only the skin was sutured above it. Near term (day 132 of gestation) fetuses were sacrificed for pathological analysis. RESULTS: There were two miscarriages and one maternal death. In total, six cases were available for pathological analysis, three in each group. In Group 1, there were adherence of the spinal cord to the scar (meningo-neural adhesion) and spinal cord architecture loss with posterior funiculus destruction and no visualization of grey matter. In Group 2, we observed in all cases formation of a neo-dura mater, separating the nervous tissue from adjacent muscles, and preserving the posterior funiculus and grey matter. CONCLUSION: The new simplified technique was better than the classic neurosurgical technique. It preserved the nervous tissue and prevented the adherence of the spinal cord to the scar. This suggests the current technique used for the correction of spina bifida in humans may need to be reassessed.

A new bilayer chitosan scaffolding as a dural substitute: experimental evaluation

OBJECTIVE

To evaluate whether bilayer chitosan scaffolding (BChS) can provide a watertight dural closure and permit regeneration by fibroblasts in an experimental in vivo model.

METHODS

In the in vitro phase, BChS was elaborated and the following characteristics were evaluated: pore size, thickness, water absorption capacity, tensile strength, strain, and toughness. In the second in vivo phase, 27 durectomized New Zealand rabbits were randomly assigned into three duraplasty groups with autologous dura, collagen matrix (CM), or BChS. In all groups, fluid leakage pressure was measured at 10, 21, or 180 days. Histology response to regeneration was evaluated through hematoxylin and eosin stain.

RESULTS

BChS was standardized to obtain bilayer scaffoldings with a nonporous layer and a porous layer. The pore size was 10 μm, total thickness was 400 μm, strain was 57.8%, and tensile strength was 5.5 gr/mm(2). The physical characteristics of BChS allowed dural closure without cerebrospinal fluid (CSF) leak. There were no differences in fluid leakage pressures between the BChS, dura, and CM groups. Histologic analysis showed fibroblast migration with adequate dural regeneration.

CONCLUSIONS

BChS is an ideal alternative for a watertight dural closure because it can be sutured, and it induces organized regeneration with fibroblasts without evidence of fibrosis.

Bacterial cellulose-hydroxyapatite nanocomposites for bone regeneration

The aim of this study was to develop and to evaluate the biological properties of bacterial cellulose-hydroxyapatite (BC-HA) nanocomposite membranes for bone regeneration. Nanocomposites were prepared from bacterial cellulose membranes sequentially incubated in solutions of CaCl₂ followed by Na₂HPO₄. BC-HA membranes were evaluated in noncritical bone defects in rat tibiae at 1, 4, and 16 weeks. Thermogravimetric analyses showed that the amount of the mineral phase was 40%–50% of the total weight. Spectroscopy, electronic microscopy/energy dispersive X-ray analyses, and X-ray diffraction showed formation of HA crystals on BC nanofibres. Low crystallinity HA crystals presented Ca/P a molar ratio of 1.5 (calcium-deficient HA), similar to physiological bone. Fourier transformed infrared spectroscopy analysis showed bands assigned to phosphate and carbonate ions. In vivo tests showed no inflammatory reaction after 1 week. After 4 weeks, defects were observed to be completely filled in by new bone tissue. The BC-HA membranes were effective for bone regeneration.

Results of the Prospective, Randomized, Multicenter Clinical Trial Evaluating a Biosynthesized Cellulose Graft for Repair of Dural Defects

BACKGROUND

After intradural cranial surgery, a dural substitute is often required for dural closure. Although preferred, limitations of autograft include local availability and additional surgical site morbidity. Thus, allografts, xenografts, and synthetics are frequently used.

OBJECTIVE

To report 6-month results of a randomized, controlled trial of a biosynthesized cellulose (BSC) composed duraplasty device compared with commercially available dural replacements.

METHODS

A total of 99 patients (62 BSC; 37 control) were treated on protocol, using a 2:1 (BSC:control) blocked randomization schedule. Physical examinations were performed pre- and postoperatively within 10 days and at 1, 3, and 6 months. Magnetic resonance imaging was performed preoperatively and at 6 months. The primary study endpoint was the absence of pseudomeningocele and extracerebral fluid collection confirmed radiographically and the absence of cerebrospinal fluid fistula at 6 months.

RESULTS

At 6 months, the primary hypothesis, noninferiority of the BSC implant compared with the control group, was confirmed (P = .0206). Overall success was achieved by 96.6% of BSC and 97.1% of control patients. No significant difference was revealed between treatment groups for surgical site infection (P = 1.0000) or wound healing assessment (P ≥ .3685) outcomes, or radiologic endpoints (P ≥ .4061). Device strength and seal quality favored BSC.

CONCLUSION

This randomized, controlled trial establishes BSC as noninferior to commercially available dural replacement devices. BSC offers a hypothetical advantage concerning prion and other infectious agent exposure; superior handling qualities are evident. Longer term data are necessary to identify limitations of BSC and its potential equivalence to the gold standard of pericranium.

Clinical experience with a novel bovine collagen dura mater substitute

Dural substitutes are used to achieve watertight closure of the dura mater when adequate closure is not possible. The purpose of this study was to evaluate the efficacy and safety of a new collagen matrix dural substitute (Duradry, Technodry, Belo Horizonte MG) in the repair or expansion of cranial and spinal dura mater. METHOD: Thirty patients, operated on between March and September, 2008, were studied. Surgical records were reviewed for sex, age, location of graft, technique, and presence of fistula or infection. The patients were followed up for at least 3 months, and presence of complications, such as cerebrospinal fluid leakage, infection, asseptic meningitis hydrocephalus, pseudomeningocele, was analyzed. RESULTS: Only one patient presented cerebrospinal fluid fistula. No patients presented wound infections, hydrocephalus, pseudomenigocele, meningites, brain abscesses or signs of toxicity related to the dural substitute. CONCLUSION: The new dural substitute used in this study is effective and safe, and the initial results are similar to those of other dural substitutes reported in the literature.

Development of Bacterial Cellulose Nanocomposites

The development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment.

Tissue-engineered conduit using urine-derived stem cells seeded bacterial cellulose polymer in urinary reconstruction and diversion

The objective of this study was to generate bacterial cellulose (BC) scaffolds seeded with human urine-derived stem cells (USC) to form a tissue-engineered conduit for use in urinary diversion. Microporous BC scaffolds were synthesized and USC were induced to differentiate into urothelial and smooth muscle cells (SMC). Induced USC (10(6) cells/cm(2)) were seeded onto BC under static and 3D dynamic (10 or 40 RPM) conditions and cultured for 2 weeks. The urothelial cells and SMC derived from USC formed multilayers on the BC scaffold surface, and some cells infiltrated into the scaffold. The urothelium derived from USC differentiation expressed urothelial markers (uroplakin Ia and AE1/AE3) and the SMC expressed SMC markers (α-smooth muscle actin and desmin). In addition, USC/BC scaffold constructs were implanted into athymic mice, and the cells were tracked using immunohistochemical staining for human nuclear antigen. In vivo, the cells appeared to differentiate and express urothelial and SMC markers. In conclusion, porous BC scaffolds allow 3 dimensional growth of USC, leading to formation of a multilayered urothelium and cell-matrix infiltration. Thus, cell-seeded BC scaffolds hold promise for use in tissue-engineered urinary conduits for urinary reconstruction.

In vivo and in vitro evaluation of an Acetobacter xylinum synthesized microbial cellulose membrane intended for guided tissue repair

BACKGROUND

Barrier materials as cellulose membranes are used for guided tissue repair. However, it is essential that the surrounding tissues accept the device. The present study histologically evaluated tissue reaction to a microbial cellulose membrane after subcutaneous implantation in mice. Furthermore, the interaction between mesenchymal stem cells and the biomaterial was studied in vitro to evaluate its ability to act as cellular scaffold for tissue engineering.

METHODS

Twenty-five Swiss Albino mice were used. A 10 x 10 mm cellulose membrane obtained through biosynthesis using Acetobacter xylinum bacteria was implanted into the lumbar subcutaneous tissue of each mouse. The mice were euthanatized at seven, 15, 30, 60, and 90 days, and the membrane and surrounding tissues were collected and examined by histology.

RESULTS

A mild inflammatory response without foreign body reaction was observed until 30 days post-surgery around the implanted membrane. Polarized microscopy revealed that the membrane remained intact at all evaluation points. Scanning electron microscopy of the cellulose membrane surface showed absence of pores. The in vitro evaluation of the interaction between cells and biomaterial was performed through viability staining analysis of the cells over the biomaterial, which showed that 95% of the mesenchymal stem cells aggregating to the cellulose membrane were alive and that 5% were necrotic. Scanning electron microscopy showed mesenchymal stem cells with normal morphology and attached to the cellulose membrane surface.

CONCLUSION

The microbial cellulose membrane evaluated was found to be nonresorbable, induced a mild inflammatory response and may prove useful as a scaffold for mesenchymal stem cells.

Biomechanical evaluation of microbial cellulose (Zoogloea sp.) and expanded polytetrafluoroethylene membranes as implants in repair of produced abdominal wall defects in rats

PURPOSE: To evaluate the Load of Rupture of implants of membranes of microbial cellulose (Zoogloea sp.) and extended polytetrafuoroethylene in sharp defects of abdominal wall of rats. METHODS: Sixty Wistar male rats, with a mean weight of 437,7g ± 40,9, anesthetized by a mixture of ketamine (5mg/100g) and xylazine (2mg/100g), were submitted to a rectangular (2x3cm) excision of the abdominal wall, including fascia, muscle and peritoneum, and treated with membranes of microbial cellulose (MC) (MC Group- 30 animals) or extended polytetrafluoroethylene (ePTFE) (ePTFE Group- 30 animals). Each group was subdivided in 14th POD, 28th POD and 60th POD Subgroups. Under anesthesia, animals were submitted to euthanasia at 14th POD, 28th POD and 60th POD for evaluation of Load of Rupture. RESULTS: Load of Rupture levels were significantly elevated (p<0, 05) among 14th, 28th and 60th postoperative days from each Group. When compared between groups, values of Load of Rupture were significantly larger (p<0, 05) in ePTFE Group than in MC Group. CONCLUSION: Resistance to strength at implant/host interface was more pronounced in PTFEe Group than in MC Group.

Collagen-only biomatrix as a novel dural substitute. Examination of the efficacy, safety and outcome: clinical experience on a series of 208 patients

OBJECTIVES

Dural replacement materials and other measures can provide an effective barrier between the subarachnoid compartment and the extradural space when a watertight closure of the patient's own dura is not possible.

PATIENTS AND METHODS

We evaluated the efficacy and safety of a novel collagen-derived dural substitute on a series of 208 patients undergoing a variety of neurosurgical procedures.

RESULTS

No patients experienced any local or systemic complications nor toxicity related to the dural patch. No patients experienced post-operative CSF fistula except for one. Post-operative MRIs showed signs of moderate inflammatory response in only one patient, who did not present any post-operative clinical symptom nor neurological deficits. Three patients underwent reoperation for bone flap repositioning after decompressive craniectomy: in these cases, the dural substitute appeared to have promoted a satisfactory dural regeneration, as confirmed by the histological studies. Furthermore, in such cases no or minimal adherences with the other tissues and the brain cortex was observed.

CONCLUSIONS

The new collagen-only biomatrix is a safe and effective dural substitute for routine neurosurgical procedures. The absence of local and systemic toxicity or complications, and the scarce promotion of adherences and inflammation, make this material appealing for its use as dural substitute even in cases when a needed re-operation is anticipated.

Biosynthetic cellulose induces the formation of a neoduramater following pre-natal correction of meningomyelocele in fetal sheep

PURPOSE: The aim of this study was to compare the effectiveness of two dura-mater substitutes, namely human acellular dermal matrix (HADM) and biosynthetic cellulose (BC), in repairing, in utero, surgically-induced meningomyelocele (MMC) in fetal sheep. METHODS: A neural tube defect was created at 74-77 days gestation in 36 fetal sheep. They were divided into 3 groups, the control group that did not receive pre-natal corrective surgery, and the other two groups that received corrective surgery using HADM (Group A) or BC (Group B). Both materials were used as a dura-mater substitutes between the neural tissue and the sutured skin. Correction was performed at gestation day 100 and the fetuses were maintained in utero until term. Sheep were sacrificed on gestation day 140. The fetal spine was submitted to macro and microscopic analysis. At microscopy, adherence of the material to the skin and neural tissue was analyzed. RESULTS: In the initial phase (pilot), experimentally-induced MMC was performed on 11 fetuses and 4 survived (37%). In the second phase (study), 25 fetuses received surgery and 17 survived (68%). In the study group, 6 fetuses did not undergo repair (control group), 11 cases were submitted to corrective surgery (experimental group) and one fetal loss occurred. Of the surviving cases in the experimental group, 4 constituted Group A and 6 in Group B. Macroscopically, skin and underlying tissues where easily displaced from the BC in all cases it was used; in contrast, HADM adhered to these tissues. To compare the adherence, 4 cases from Group A and 4 in Group B were studied. We observed adherence, host cell migration and vessel proliferation into the HADM all sections from Group A and this aspect was not present in any cases in Group B (p < 0.05). In Group B, we also observed that a new fibroblast layer formed around the BC thus protecting the medulla and constituting a "neoduramater". CONCLUSION: The use of BC seems to be more adequate as a dura-mater substitute to cover the damaged neural tissue than HADM. It seems promising for use in the in utero correction of MMC because to does not adhere to neural tissue of superficial and deep layers ("tethered spinal cord"). Thus, BC minimizes the mechanical and chemical intrauterine damage to the spinal medulla.

Statistical analysis of optimal culture conditions for Gluconacetobacter hansenii cellulose production

AIM

The purpose of this study was to analyse the effects of different culture parameters on Gluconacetobacter hansenii (ATCC 10821) to determine which conditions provided optimum cellulose growth.

METHODS AND RESULTS

Five culture factors were investigated: carbon source, addition of ethanol, inoculation ratio, pH and temperature. jmp Software (SAS, Cary, NC, USA) was used to design this experiment using a fractional factorial design. After 22 days of static culture, the cellulose produced by the bacteria was harvested, purified and dried to compare the cellulose yields. The results were analysed by fitting the data to a first-order model with two-factor interactions.

CONCLUSIONS

The study confirmed that carbon source, addition of ethanol, and temperature were significant factors in the production of cellulose of this G. hansenii strain. While pH alone does not significantly affect average cellulose production, cellulose yields are affected by pH interaction with the carbon source. Culturing the bacteria on glucose at pH 6.5 produces more cellulose than at pH 5.5, while using mannitol at pH 5.5 produces more cellulose than at pH 6.5. The bacteria produced the most cellulose when cultured on mannitol, at pH 5.5, without ethanol, at 20 degrees C. Inoculation ratio was not found to be a significant factor or involved in any significant two-factor interaction.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings give insight into the conditions necessary to maximize cellulose production from this G. hansenii strain. In addition, this work demonstrates how the fractional factorial design can be used to test a large number of factors using an abbreviated set of experiments. Fitting a statistical model determined the significant factors as well as the significant two-factor interactions.

The Future Prospects of Microbial Cellulose in Biomedical Applications

Microbial cellulose has proven to be a remarkably versatile biomaterial and can be used in wide variety of applied scientific endeavors, such as paper products, electronics, acoustics, and biomedical devices. In fact, biomedical devices recently have gained a significant amount of attention because of an increased interest in tissue-engineered products for both wound care and the regeneration of damaged or diseased organs. Due to its unique nanostructure and properties, microbial cellulose is a natural candidate for numerous medical and tissue-engineered applications. For example, a microbial cellulose membrane has been successfully used as a wound-healing device for severely damaged skin and as a small-diameter blood vessel replacement. The nonwoven ribbons of microbial cellulose microfibrils closely resemble the structure of native extracellular matrices, suggesting that it could function as a scaffold for the production of many tissue-engineered constructs. In addition, microbial cellulose membranes, having a unique nanostructure, could have many other uses in wound healing and regenerative medicine, such as guided tissue regeneration (GTR), periodontal treatments, or as a replacement for dura mater (a membrane that surrounds brain tissue). In effect, microbial cellulose could function as a scaffold material for the regeneration of a wide variety of tissues, showing that it could eventually become an excellent platform technology for medicine. If microbial cellulose can be successfully mass produced, it will eventually become a vital biomaterial and will be used in the creation of a wide variety of medical devices and consumer products.

Repair of the dura mater with processed collagen devices

BACKGROUND

We evaluated in a canine duraplasty model how specific differences in device physicomechanical properties, porosity, and crosslinking influenced the biological performance of three processed collagen dural substitutes.

METHODS

Three collagen dural substitutes were studied: Dura-Guard, DuraGen, and Durepair. The initial strength, stiffness, and suture retention force were measured using standard mechanical test methods. The relative pore sizes of each device were assessed with a scanning electron microscope. Differential scanning calorimetry was used to measure their respective collagen denaturation temperatures. The biologic response and performance of the materials were evaluated via an acute (1 month) and long-term (3 and 6 months) canine bilateral duraplasty study.

RESULTS

The mechanical properties of Dura-Guard and Durepair were similar to native dura. We could not quantify the mechanical properties of DuraGen because of its fragile nature. The denaturation temperature of DuraGen and Dura-Guard differed significantly from that reported for native collagens. The denaturation temperature of Durepair was comparable with the values reported for native collagens. All three materials were tolerated well by the animals. DuraGen did not maintain its structural integrity beyond 1 month. Dura-Guard and Durepair persisted for 6 months. Durepair was populated by fibroblasts and blood vessels, whereas Dura-Guard was not.

CONCLUSIONS

The three dural substitutes tested were found to be safe and effective in healing surgically created defects in the dura mater. Although each of these dura substitutes are composed of collagen, differences in the collagen source and processing influenced device physicomechanical properties, porosity, and the nativity of the collagen polymer. These measured differences influenced device intraoperative handling and installation as well as the post-operative biological response, where differences in device resorption, cell penetration, vascularization, and collagen remodeling were observed.

The effects of free fat graft or cellulose membrane implants on laminectomy membrane formation in dogs

The purpose of this study was to determine the effect of cellulose membrane or free fat grafts (FFG) on laminectomy membrane (LM) formation. Eighteen dogs were randomly divided into three groups of six dogs. All dogs underwent a modified dorsal laminectomy on T(13)-L(1). The laminectomy defect was left uncovered in the control group but either a FFG or a cellulose membrane implant was provided in the other two groups. The dogs were evaluated through neurological examination, myelography, macroscopic roundness index of spinal cord and histological evaluations of epidural fibrosis and spinal cord. The results showed a significant difference between the control and the FFG group, with the FFG causing neurological deficits and spinal cord compression as assessed by the roundness index of the spinal cord. Both FFG and cellulose membrane were partially effective in preventing LM formation. The use of FFG was associated with a high rate of significant neurological complications and spinal cord lesions.

Autologous tissues for dural grafting in children: a report of 56 cases

BACKGROUND

Diverse materials have been used for dural closure, including grafts of cadaveric origin. Some 168 cases of Creutzfeldt-Jakob disease have been reported following the implant of human dura mater. A few publications have addressed the use of dural grafts in children, but none has analyzed the feasibility of autologous tissues for this purpose.

AIM

Since 1994, the authors have utilized autologous tissues for dural grafting in children undergoing neurosurgical procedures, aimed at studying the feasibility of its use in this age group.

MATERIAL AND METHODS

We studied 56 children submitted to neurosurgical procedures who underwent an implant of a patch of autologous tissue for dural closure. Epidemiological, clinical, and neuroimaging data were processed using statistical methods.

RESULTS

The study group was composed of 29 boys and 27 girls, with ages ranging from 1 month to 17 years (mean 7.6 years). The procedures corresponded to lesions at the posterior cranial fossa (n = 41), supratentorial cranial compartment (n = 12), and spine (n = 3). Seventy-five percent of the children had no complication. Four patients had adverse effects unrelated to dural grafting, while ten children had complications that might be associated with it. The most frequent complication was pseudomeningocele (n = 6), followed by infection (n = 3) and CSF leak (n = 1). Although hydrocephalus seemed to have an influence on the occurrence of complications, their incidence in patients without hydrocephalus did not differ statistically.

CONCLUSIONS

Autologous grafts of fascia or pericranium can be safely used for dural reconstruction in children. Given the reported complications associated with the use of foreign materials for duraplasty, the authors recommend the use of autologous tissues for dural repair, reserving other types of dural grafts for cases in which its usage is unavoidable.

Suturing technique and the integrity of dural closures: an in vitro study

OBJECTIVE

The watertight closure of the dura mater is fundamental to intracranial procedures in neurosurgery. Nevertheless, for any given operator and type of suture, it is still not certain which suturing technique affords the most watertight dural closure. We have developed a laboratory model that allows us to compare the pressures at which dural closures leak when different suturing techniques are used.

METHODS

Human cadaveric dura was secured to a glass cylinder filled with colored saline. By application of force to a bag of saline attached to the cylinder, the pressure at which sutured dural incisions leak can be recorded. Using this method, we have compared the closure of 2-cm dural incisions with 3-0 silk using the following techniques (10 per group): 1) interrupted simple, 2) running simple, 3) running locked, and 4) interrupted vertical mattress. We have also compared the closure of 1- x 3-cm dural windows with cadaveric dura and 3-0 silk using the same suturing techniques (10 per group).

RESULTS

The pressure at which 2-cm linear dural incisions leaked was significantly higher when they were closed with the interrupted simple suturing technique (P < 0.05). There was no significant difference among the different suturing techniques when they were used to close a 1- x 3-cm dural window with a duraplasty. Overall, the pressures at which sutured linear dural incisions leaked were higher than the pressures at which sutured dural windows closed with duraplasties leaked.

CONCLUSION

In the experimental model described, an interrupted simple suturing technique affords the most watertight dural closure for linear incisions, whereas no suturing technique proved advantageous for the closure of a duraplasty.

Cerebrospinal Fluid Leaks of Temporal Bone Origin: Etiology and Management

BACKGROUND

Cerebrospinal fluid (CSF) leaks of the temporal bone region require surgical treatment as they pose life-threatening risks such as meningitis.

AIM

The aim of the study was to determine the surgical outcome depending on different operation techniques and grafts.

METHOD

We performed a retrospective review of 28 cases of CSF leaks, operated in our department from 1983 to 2002. After a mean follow-up of 8 years, patients were interviewed concerning otorrhea or rhinorrhea and meningitis. In this context, our management of CSF leaks is presented.

RESULTS

The CSF leak had arisen spontaneously (n = 3), traumatically (n = 6) or postoperatively (n = 19). The surgical CSF leak repairs were performed via a transmastoid (n = 13), a middle fossa (n = 11) or a combined (n = 4) approach. Surgical outcome was independent on the used graft. CSF leak could be sealed in 25 of 28 cases. Only 3 patients suffered from recurrences. Meningitis or other complications did not occur.

CONCLUSIONS

Comparing different techniques and grafts, there were no differences in the surgical outcome.

Duraplasty: our current experience

BACKGROUND

A large variety of biologic and artificial materials have been suggested as dural substitutes. However, no ideal material for dural repair in neurosurgical procedures has been identified. The authors report their experience with Tutoplast processed dura and pericardium.

METHODS

This study is designed to evaluate Tutoplast dura and pericardium. The study population was composed of 250 consecutive patients who underwent cerebral duraplasty with these homologous materials between 1996 and 1998. The average follow-up was 5.4 years.

RESULTS

We have observed only four complications with uncertain relationship with the dural implant. These resulted in complete recovery.

CONCLUSIONS

We support the efficacy and safety of this natural dural substitute treated with Tutoplast method.

Evaluation of a novel propylene oxide—treated collagen material as a dural substitute

Object. The authors evaluated a new non—cross-linked, propylene oxide—treated, acellular collagen matrix for use as a dural substitute in rabbits. They then compared this material to a commonly used dural substitute as well as to native dura mater used during primary closure.

Methods. Forty-six rabbits were randomly assigned to eight groups of five or six rabbits each. These groups differed according to the type of closure material that was used during surgery (native dura, control dural substitute, or experimental dural substitute) and the duration of convalescence. At the end of the experiment, the tightness of the duraplasty was assessed in each live rabbit by continuous infusion of fluid into the cisterna magna until leakage was detected. The animals were killed and each specimen was sectioned and studied histologically. The authors found that the experimental dural substitute was safe in animals for this application, that it held sutures well, and that a watertight closure was usually achieved. There were fewer adhesions between the experimental material and neural tissue was less likely to adhere to the cranium than the control graft. Histological examination showed that the experimental material had slightly more spindle cells and vascularity than the control graft.

Conclusions. The experimental graft material has several features that make it an attractive candidate for use as a dural substitute.

Bovine pericardium for dural graft: clinical results in 22 patients

BACKGROUND

Bovine pericardium has widely been used for grafts in cardiac surgery and seems to have suitable properties for use as a dural graft. We report our experience of using locally processed bovine pericardium for dural grafts in 22 patients undergoing cranial operations.

METHODS

22 patients were analysed prospectively and followed-up for a maximum 3 years. All available records and information regarding the indication for grafting, graft size, complications and outcome were collected and analysed.

RESULTS

Indications for grafting included neurosurgical, tumour, congenital and trauma patients. Outcomes were classified as good or excellent in 20 patients, whereas in two patients death was not related to surgical closure but more to malignant intracranial hypertension. In no patient was the dural graft a significant factor in the outcome. Bovine pericardium was found to be easily sutured and watertight using standard 4-0 silk suture. This material is relatively inexpensive compared to other non-synthetic grafts.

CONCLUSION

In this clinical assessment, our bovine pericardium better known as Lyolemb was found to be an excellent dural graft material for local and eventual international consumption.