The use of advanced biological and tissue-engineered wound products

This article aims to reintroduce readers to biologically based and tissue-engineered wound management products. Indications for their use in clinical practice are suggested. It also examines two well-established wound management interventions, topical negative pressure therapy and larval therapy, which could have a positive effect on the outcome of biologically based and tissue-engineered wound management products.

Sculptra: the New Three-Dimensional Filler

Sculptra, the synthetic injectable poly-l-lactic acid (PLLA), is a revolutionary three-dimensional filler lasting 18 to 24 months. This unique volumizing agent is best used to globally restore volume to the lower two thirds of the face in patients who have lipoatrophy. Sculptra is a biocompatible, biodegradable, and nonimmunogenic derivative of the alpha-hydroxy-acid family. The size and the slow degradation kinetics of PLLA microparticles act as a stimulus for collagen production, providing lasting volume enhancement in lipoatrophy patients.

An Overview of Permanent and Semipermanent Fillers

The demand for safe, effective, long-lasting, biocompatible dermal filler materials is increasing. Many products that include synthetic polymers and autologous tissue have emerged that attempt to meet these criteria. An overview of injectable permanent fillers, including ArteFill, Aquamid, and silicone, and semipermanent fillers, including Radiesse, Sculptra, and autologous fat, is presented. A discussion of their composition, histologic characteristics, antigenicity, U.S. Food and Drug Administration approval status, indications for use, efficacy, injection technique, and adverse effects is provided.

Injectable Poly-L-Lactic Acid (Sculptra): Technical Considerations in Soft-Tissue Contouring

BACKGROUND

Poly-L-lactic acid gained U.S. Food and Drug Administration approval for use in human immunodeficiency virus-related facial lipoatrophy in August of 2004. Since that time, it has become available for use in the United States for human immunodeficiency virus facial lipoatrophy patients and for off-label uses in other areas for soft-tissue contouring. This article is intended to enumerate reconstitution, injection techniques, management, and avoidance of complications.

METHODS

The authors have pooled their experiences to arrive at a consensus opinion for recommendations on treatment protocols for injectable poly-L-lactic acid use.

RESULTS

This article prescribes techniques to achieve safer, consistent results while minimizing risks of complications with injectable poly-L-lactic acid. Although the product has been used widely in Europe since 1999, physicians in the United States have only recently begun to explore the uses of Sculptra as a volumizing agent in the face and the body. U.S. physicians have benefited from the European experience with this product, including early problems secondary to overaggressive use, low-volume reconstitution, higher volume injection of product at one session, and inadequate time between injection sessions.

CONCLUSIONS

The authors therefore have opted for a more conservative approach in their treatment recommendations. Higher volume dilution (8 to 12 cc), fewer vials used at each session, injections placed in the subcutaneous plane without any product being placed in the dermis, adequate time between injection sessions (at least 6 weeks), and postinjection patient massage should decrease the risks and avoid the potential complications associated with poly-L-lactic acid soft-tissue augmentation.

Expression of matrix metalloproteinases and growth factors in diabetic foot wounds treated with a protease absorbent dressing

Wound healing in diabetes is impaired, and nonhealing ulceration represent clinically relevant complications. Persistently high levels of matrix metalloproteases (MMPs) contribute to wound chronicity. Thus, the topical use of protease inhibitors might influence wound healing and promote transition from a chronic to an acute wound.

METHODS

In this study, 33 patients with chronic diabetic foot lesions (stage 2a of the University of Texas Wound Classification system) were included. Fifteen patients received redundant "good standard wound care." In addition, 18 patients were treated with a protease inhibitory modulating matrix (the OCR/collagen Promogran matrix, Ethicon) with dressings changed on a daily basis. Prior to treatment and at 4 and 8 days after treatment, two 3-mm punch biopsies were taken from the center of the wounds and analyzed using ELISA techniques for MMPs, tissue inhibitor of MMP-2 (TIMP-2), and interleukin-1beta (IL-1beta) levels. In addition, mRNA levels of MMPs as well as IL-1beta and TNF-alpha were detected using quantitative real-time polymerase chain reaction (TaqMan, Applied Biosystems, Weiterstadt, Germany).

RESULTS

No differences were detected between both groups and at the three time points for the mRNA levels of MMPs as well as of IL-1beta and TNF-alpha. In addition, MMP levels in wound tissue (analyzed by ELISA) were also not significantly different between both groups. However, IL-1beta was increased on day 8 in the treatment group (P=.01) only. Interestingly, we found a significant reduction of the MMP-9/TIMP-2 ratio in the group being treated with the ORC/collagen. These wounds exhibited a more rapid healing rate when treated with the ORC/collagen matrix.

CONCLUSIONS

The local treatment with a protease inhibitor has a beneficial effect on wound healing. In contrast to the data on wound fluid, our study demonstrated for the first time the unaltered mRNA levels of MMPs during treatment with a protease inhibitory modulating matrix. At the cellular level, MMPs were also not statistically different. However, the more relevant ratio of MMP-9/TIMP-2 was decreased in the treatment group. An equally important finding was that we did not detect a compensatory increase in the MMP-RNA expression even though wound size was clearly reduced.

Patient safety considerations regarding dermal filler injections

Today's population is seeking procedures that enhance or improve its appearance, that require little or no downtime, and that provide immediate results. Dermal filler injections are among the top five procedures performed for this purpose. Patient safety must remain the ultimate goal of any practitioner delivering such procedures. This column will examine pertinent safety considerations in relation to the delivery of dermal filler injections.

Vaginal microbicides: detecting toxicities in vivo that paradoxically increase pathogen transmission

BACKGROUND

Microbicides must protect against STD pathogens without causing unacceptable toxic effects. Microbicides based on nonoxynol-9 (N9) and other detergents disrupt sperm, HSV and HIV membranes, and these agents are effective contraceptives. But paradoxically N9 fails to protect women against HIV and other STD pathogens, most likely because it causes toxic effects that increase susceptibility. The mouse HSV-2 vaginal transmission model reported here: (a) Directly tests for toxic effects that increase susceptibility to HSV-2, (b) Determines in vivo whether a microbicide can protect against HSV-2 transmission without causing toxicities that increase susceptibility, and (c) Identifies those toxic effects that best correlate with the increased HSV susceptibility.

METHODS

Susceptibility was evaluated in progestin-treated mice by delivering a low-dose viral inoculum (0.1 ID50) at various times after delivering the candidate microbicide to detect whether the candidate increased the fraction of mice infected. Ten agents were tested - five detergents: nonionic (N9), cationic (benzalkonium chloride, BZK), anionic (sodium dodecylsulfate, SDS), the pair of detergents in C31G (C14AO and C16B); one surface active agent (chlorhexidine); two non-detergents (BufferGel, and sulfonated polystyrene, SPS); and HEC placebo gel (hydroxyethylcellulose). Toxic effects were evaluated by histology, uptake of a 'dead cell' dye, colposcopy, enumeration of vaginal macrophages, and measurement of inflammatory cytokines.

RESULTS

A single dose of N9 protected against HSV-2 for a few minutes but then rapidly increased susceptibility, which reached maximum at 12 hours. When applied at the minimal concentration needed for brief partial protection, all five detergents caused a subsequent increase in susceptibility at 12 hours of approximately 20-30-fold. Surprisingly, colposcopy failed to detect visible signs of the N9 toxic effect that increased susceptibility at 12 hours. Toxic effects that occurred contemporaneously with increased susceptibility were rapid exfoliation and re-growth of epithelial cell layers, entry of macrophages into the vaginal lumen, and release of one or more inflammatory cytokines (Il-1beta, KC, MIP 1alpha, RANTES). The non-detergent microbicides and HEC placebo caused no significant increase in susceptibility or toxic effects.

CONCLUSION

This mouse HSV-2 model provides a sensitive method to detect microbicide-induced toxicities that increase susceptibility to infection. In this model, there was no concentration at which detergents provided protection without significantly increasing susceptibility.

A novel adsorbent of circulating bacterial toxins and cytokines: the effect of direct hemoperfusion with CTR column for the treatment of experimental endotoxemia

OBJECTIVES

The current study examined the ability of a new adsorbent, CTR, to remove enterotoxins, toxic shock syndrome toxin-1 (TSST-1), and cytokines from blood and/or serum in vitro and the effects of the extracorporeal treatment with CTR column on mortality rate and inflammatory responses to endotoxic shock in vivo.

DESIGN

Laboratory investigation.

SETTING

University and company experimental laboratory.

MATERIALS

CTR is composed of porous cellulose beads to which a hydrophobic organic compound with a hexadecyl alkyl chain has been covalently bound to the surface as a ligand. Human/bovine serum and human blood samples in vitro and Male Wistar rats were used.

INTERVENTIONS

CTR's ability to adsorb bacterial toxins and cytokines related to sepsis in serum and/or blood was examined with an in vitro batch adsorption protocol. In vivo, male Wistar rats were anesthetized and assigned to one of three groups (n=14 per group): Escherichia coli endotoxin (15 mg/kg intravenously) alone (endotoxemic), apheresis with control column without CTR for 120 mins (control column), or extracorporeal treatment with CTR column for 120 mins (CTR treatment).

MEASUREMENTS AND MAIN RESULTS

With use of the CTR adsorbent, the adsorption rates were 50% to 90% for enterotoxins, TSST-1, and cytokines such as TNF-alpha and interleukin (IL)-6 in the batch tests. In vivo, the mortality rates at 8 hrs after endotoxin injection were 92%, 92%, and 14% for the endotoxemic, control column, and CTR treatment groups, respectively. Hypotension and elevated plasma cytokine concentrations and the infiltration of neutrophils of the lungs were less conspicuous in the CTR treatment group than in the other two groups.

CONCLUSIONS

CTR, a novel adsorbent, effectively adsorbed small- to middle-sized proteins, such as cytokines, enterotoxins, and TSST-1 in vitro. Direct hemoperfusion apheresis with CTR column reduced mortality and had inhibitory effects on the inflammatory responses during endotoxemia in vivo. These findings suggest that extracorporeal blood purification with CTR column may be available to use for patients with sepsis and/or endotoxemia.

Microtensile bond strengths of composite to dentin treated with desensitizer products

PURPOSE

This study was designed to analyze the influence of desensitizing procedures on dentin bond strength.

MATERIALS AND METHODS

Forty bovine incisors were used, divided into four groups (n = 10): G1: control; G2: Gluma Desensitizer (Heraeus Kulzer); G3: Oxa-Gel (Art-Dent); G4: low-intensity laser (MMOptics). The buccal surface was wet ground flat with 180-, 400- and 600-grit silicon carbide abrasive paper to expose midcoronal dentin and create a uniform surface. After the application of the desensitizing agents to the exposed dentin, the specimens were etched with 35% phosphoric acid for 30 s, and an adhesive (Single Bond) was applied and light cured. A 4-mm high crown of composite resin (Filtek Z250) was then built up. Specimens were trimmed to an hourglass shape with cross sections of 1 mm2. Each specimen was individually fractured by a microtensile testing machine at a crosshead speed of 0.5 mm/min. The data, recorded in MPa, were analyzed with one-way ANOVA and the Duncan test (p = 0.05).

RESULTS

Specimens treated with dentin desensitizers (except Gluma) yielded significantly lower mean bond strengths than nontreated control specimens. The mean values in MPa (+/- SD) were: G1: 13.4 (6.2); G2: 13.2 (4.8); G3: 7.15 (4.3); G4: 7.21 (4.6).

CONCLUSIONS

Among the desensitizing agents studied, only Gluma Desensitizer did not detrimentally influence the bond strength values. It is a useful material for dentin desensitization.

A double blind, placebo controlled trial of inert cellulose powder for the relief of symptoms of hay fever in adults

OBJECTIVE

An inert cellulose powder has been on sale in the UK since 1994 as a remedy for hay fever but no scientific trials have been conducted previously. It is applied to the inside of the nose where it forms a gelatinous coating. The principal aim was to determine if there is a significant difference in the amount and type of rescue medication required for adult hay fever sufferers to control their symptoms while using either the inert cellulose powder or a placebo. The second objective was to see whether the cellulose powder resulted in an improvement in symptom control.

RESEARCH DESIGN

A double blind, placebo controlled study was conducted of 97 adult hay fever sufferers, over the grass pollen season of 2004. Participants (selectively recruited to be living within the catchment area of a 50-km radius from Worcester, UK) were assigned randomly to two groups (A, Active and B, Placebo) matched by age by decades and gender. Of those completing the trial, group A had 19 males and 28 females and group B had 21 males and 29 females. There were no significant differences between the groups in age distributions, severity of symptoms over the last 2 years or in medication taken. They completed daily symptom diary score cards and were allowed to take any medications they wished in addition to the inert cellulose powder or placebo because medication use was taken as an outcome measure. Results were analysed in relation to pollen counts.

RESULTS

Significant differences were found in the amounts of rescue medication taken by the active and placebo groups (p < 0.05). More people in the placebo group took rescue treatments than those in the active group. No significant differences were found (p < 0.01) between the active and placebo groups in Likert scores for any of the rhinitis nasal symptoms or in the total Likert symptom daily scores. No adverse events were reported during the study.

CONCLUSIONS

The amount of rescue medication taken by the placebo group was significantly more than that taken by the active group both overall, considering all types of medication, and also in the individual cases of antihistamines, nasal sprays and eye drops. These results provide evidence that the inert cellulose powder reduces the need to take rescue medication for the symptoms of hay fever.

[Diagnostic and therapeutic aspects of dialysis-related amyloidosis]

The definitive diagnosis of dialysis-related amyloidosis based on histologic findings suffers from invasive surgical procedure and punctual information. Imaging techniques: ultrasonography, X-ray, computed tomography or magnetic resonance are relatively nonspecific and not sensitive enough. Scintigraphy using radio-labelled beta-2-microglobulin currently represents the most specific method to noninvasively diagnosis dialysis-related amyloidosis. Available therapeutic methods include the removal of BMG and palliation of symptoms. Hemodialysis high-flux and hemodiafiltration based on convection are more effective in elimination of BMG than standard hemodialysis with diffusive transport as a dominant mechanism. Use of the adsorption columns Lixelle reduces plasma BMG concentration and leads to clinical improvement of DRA. Medical therapy consists of the use of low dose corticosteroids and non-steroidal anti-inflammatory drugs. Surgical therapy is often necessary in the late stages of DRA. Renal transplantation is still the optimal method of DRA treatment.

Evaluation of in vitro-in vivo correlation and anticonvulsive effect of carbamazepine after cogrinding with microcrystalline cellulose

PURPOSE

Carbamazepine is a poor water soluble drug and its bioavailability is limited by dissolution rate. Dissolution, serum concentration and anticonvulsive effect of the drug have been evaluated after cogrinding with microcrystalline cellulose. A cogrinding technique was used to increase the dissolution, serum concentrations and anticonvulsive effect of the drug. A novel deconvolution technique of in vitro in vivo correlation was evaluated.

METHODS

The drug coground with microcrystalline cellulose, the corresponding physical mixture, unground and ground drug powder were subjected to dissolution measurement. Coground and unground drug serum concentrations were investigated in rabbits. Also the anticonvulsive effects of the latter preparations were assessed in mice. For elucidation of observed in vitro and in vivo differences FT-IR spectroscopy, X-ray diffraction patterns and DSC thermograms of the preparations were studied.

RESULTS

The dissolution of the coground was the highest (percent dissolved in the first 20 minutes, %D20', was 97.5). The unground drug powder exhibited the lowest dissolution (%D20'=40). The difference was reflected in their corresponding area under the mean serum concentration curves between 0-16 hr (118.96 vs 54.17 microg x hr/ml) as well as protection abilities against strychnine and electrically induced seizures. The onset of tonic seizures induced by strychnine was increased between 40-140% in the case of the coground system depending on dose and time of carbamazepine administration.

CONCLUSION

Cogrinding was an effective technique in increasing carbamazepine dissolution due to reduced crystallinity as seen in X-ray pattern, enhanced wettability and decreased particle size, which in turn resulted in increased serum concentrations and its anticonvulsive effect. A novel simple deconvolusion technique not requiring intravenous data denoted as the double reciprocal area method was used to establish correlation between in vitro and in vivo parameters.

Emerging Trends and Techniques in Male Aesthetic Surgery

Cosmetic surgery has witnessed explosive growth over the past few years, and with this has come growth in male aesthetic surgery. Increases have been seen in the number of nonsurgical as well as surgical treatments. Rhinoplasty, hair transplantation, and blepharoplasty continue to be the most common surgical procedures. New trends include rapid growth in nonsurgical treatments, especially Botox Cosmetic and microdermabrasion. New fillers have expanded the options for men, including long-lasting Restylane and Radiesse. Sculptra offers a new option for correction of human immunodeficiency virus-associated lipoatrophy. Fractional photothermolysis and Thermage offer new options in resurfacing.

Reduction of postoperative adhesions after laparoscopic gynecological surgery with Oxiplex/AP Gel⁎ ⁎Oxiplex/AP Gel, FzioMed, Inc., San Luis Obispo, California.: a pilot study

OBJECTIVE

To determine whether Oxiplex/AP Gel (FzioMed, San Luis Obispo, CA) was safe and preliminarily effective in reducing postsurgical adhesions after adnexal surgery by laparoscopy.

DESIGN

Prospective, multicenter, double-blind, randomized, U.S. Food and Drug Administration-monitored feasibility study.

SETTING

University and private clinics.

PATIENT(S)

Patients undergoing laparoscopic surgery with pelvic adhesions, tubal occlusion, endometriosis, and/or dermoids were randomized to receive Oxiplex/AP Gel or no further treatment after surgery.

INTERVENTION(S)

A blinded, parallel-group design was conducted at six centers. Patients (aged 18-46 years) underwent laparoscopic surgery, with second-look surgery 6-10 weeks later. Surgeries were videotaped. Oxiplex/AP Gel was used to cover adnexa and adjacent tissue.

MAIN OUTCOME MEASURE(S)

Blinded reviews of videotapes were quantitated with the American Fertility Society adhesion score (AFS score).

RESULT(S)

In 18 treatment patients, surgery was performed on 29 adnexa. Application of Oxiplex/AP Gel required approximately 90 seconds. In 10 control patients, surgery was performed on 18 adnexa. The mean baseline AFS score for each group was 8.0. At second look, treated adnexa had the same score (8.1), whereas in control adnexa the score increased (from 8.0 to 11.6). Thirty-four percent of treated adnexa increased in adhesion score, in contrast to 67% of control adnexa. There were no device-related adverse events.

CONCLUSION(S)

In this pilot study, Oxiplex/AP Gel was safe, easy to use with laparoscopy, and produced a reduction in the increase of adnexal adhesion scores.

Lubricant and razor debridement in partial thickness burn

By aiming to relieve pain from removing blisters in partial thickness burn, we tested whether the application of a sterile lubricant (KY-Jelly) on blisters and the use of a sterile razor to remove their roof can reduce algesia in humans, compared to a conventional method. A prospective randomized controlled designed study was performed on 20 patients. A visual pain scale was used by patients to evaluate pain experienced.

Cellulose acetate 1,2-benzenedicarboxylate protects against challenge with pathogenic X4 and R5 simian/human immunodeficiency virus

OBJECTIVES

To evaluate the protective efficacy of cellulose acetate 1,2-benzenedicarboxylate (CAP) formulated in a glycerol-based gel against infection with CXCR4 (X4) and CCR5 (R5) viruses in the simian/human immunodeficiency virus (SHIV)/rhesus macaque model of HIV-1 transmission.

DESIGN

Mucosal infection of non-human primates is a reasonable model for use in the investigation of HIV-1 intervention strategies.

METHODS

Rhesus macaques treated with Depo-Provera 5 weeks prior to challenge were inoculated intravaginally twice, over a period of 6 h with mixed inocula of pathogenic X4- and R5-SHIV in the presence or absence of CAP. Plasma viral load, peripheral and mucosal CD4 T cell counts as well as the genotype of the circulating virus were determined.

RESULTS

CAP protected seven of ten macaques against transmission of both X4- and R5-SHIV, reaching statistically significant values (P = 0.0256). Delayed and/or reduced virus replication, as well as blunting of peripheral and mucosal CD4 T cell loss was noted in the three macaques that were infected in the CAP treated group compared to those in the placebo group. Further, protection conferred by CAP appeared to be more effective against X4- than R5-SHIV infection.

CONCLUSIONS

CAP is protective against highly permissive challenges with X4 and R5 viruses in vivo. Research on further development of this promising compound as a candidate microbicide for the prevention of sexual HIV-1 transmission is therefore warranted.

Cellulose, modified cellulose and synthetic membranes in the haemodialysis of patients with end-stage renal disease

BACKGROUND

When the kidney fails the blood-borne metabolites of protein breakdown and water cannot be excreted. The principle of haemodialysis is that such substances can be removed when blood is passed over a semipermeable membrane. Natural membrane materials include cellulose or modified cellulose, more recently various synthetic membranes have been developed. Synthetic membranes are regarded as being more "biocompatible" in that they incite less of an immune response than cellulose-based membranes.

OBJECTIVES

To assess the effects of different haemodialysis membrane material in patients with end-stage renal disease (ESRD).

SEARCH STRATEGY

We searched MEDLINE, EMBASE, PreMEDLINE, HealthStar CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL), Biosis, SIGLE, CRIB, UK National Research Register and reference lists of relevant articles. We contacted biomedical companies, known investigators and handsearched selected journals and conference proceedings. Date of most recent search: June 2004.

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs comparing different haemodialysis membrane material in patients with ESRD.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality of studies. Data was abstracted onto a standard form by one reviewer and checked by another. Relative Risk (RR) and weighted mean difference (WMD) with 95% confidence intervals (CI)) MAIN RESULTS: Thirty two studies were identified. Pre-dialysis ss(2) microglobulin concentrations were not significantly lower in patients treated with synthetic membranes (WMD -14.67, 95% CI -33.10 to 4.05). When analysed for change in ss(2) microglobulin, a fall was only noted with high-flux membranes. The incidence of amyloid was less in patients who were dialysed for six years with high-flux synthetic membranes (one study, RR 0.03, 95% CI 0.00 to 0.54). There was a significant difference in favour of the synthetic (high-flux) membrane in comparison to cellulose membranes for triglycerides (WMD -0.66; 95% CI -1.18 to -0.14) but not for modified cellulose membranes. Dialysis adequacy measured by Kt/V was marginally higher when cellulose membranes were used (WMD -0.10; 95% CI -0.16 to 0.04), whereas synthetic membranes achieved significantly higher Kt/V values when compared with modified cellulose membranes (WMD 0.20, 95% 0.11 to 0.29) . There were no data on quality of life measures.

AUTHORS' CONCLUSIONS

We found no evidence of benefit when synthetic membranes were compared with cellulose/modified cellulose membranes in terms of reduced mortality no reduction in dialysis-related adverse symptoms. Despite the relatively large number of RCTs undertaken in this area none of the included studies reported any measures of quality of life.

A novel coating biomaterial for intracranial aneurysms: Effects and safety in extra- and intracranial carotid artery

Methyl-2-cyanoacrylate, a widely used material for coating cerebral aneurysm, was recently withdrawn. The aim of the present study was to develop an alternative coating material for cerebral aneurysm, which is safe, effective and stable within the brain. In the first experiment, an aneurysm model of the common carotid artery was produced in a rabbit by the local application of elastase. The aneurysm produced was covered by no material (Group A), a cellulose cotton sheet and conventional methyl-2-cyanoacrylate (Group B), a newly produced polyglycolic acid felt and fibrin glue (Group C), or a cellulose cotton sheet and fibrin glue (Group D). Histological examination showed that the materials resulted in the formation of tight connective tissue around the artery, and that the material was completely replaced by the connective tissue after 12 weeks. This change was found exclusively in Group C, but not in Group A or the other materials, although a temporary thickening of the intima was also observed at the site of the elastase application in Group C. In Group D, a long-term, marked thickening of the intima was observed. In the second experiment, using an intracranial internal carotid artery from a beagle, the applied polyglycolic acid felt and fibrin glue to the intracranial artery induced the formation of connective tissue around the artery that was completely absorbed 16 weeks after surgery. There were no signs of intimal thickening or of adverse reactions in nervous tissue. The present results suggest that polyglycolic acid felt and fibrin glue is a possible candidate for a safe, effective biomaterial to wrap or coat cerebral aneurysm.

Contact activation and down regulation of neutrophils by cellulose wound dressings can be prevented by radical scavengers

Neutrophil interaction with wound dressing materials was studied. A meshed non-woven cellulose was chosen as model dressing. Neutrophils isolated from human blood was added to the cellulose, and the production of reactive oxygen species was measured by luminol-amplified chemiluminescence. The respiratory burst response of the neutrophils was found to be activated upon contact with cellulose. The contact activation of the cells increased when the cellulose was oxidised with periodate, and decreased when the cellulose was reduced with cyanoborohydride, indicating that the activation of the respiratory burst response was due to carbonyl-induced stress. The contact activation of the respiratory burst response resulted in an inability of the neutrophils to respond to a secondary stimulation with zymosan. When radical scavenger enzymes were covalently bound to the cellulose, the contact activation was decreased and the ability to respond to stimuli was increased. Addition of the molecular scavenger glutathione (GSH) did not decrease the cell activation upon cellulose contact, but the cell showed an intact ability to respond to secondary stimuli after cellulose contact. In conclusion, the results show that the environmental redox potential effects neutrophils in a situations of clinical interest and that the addition of radical scavengers protects the neutrophils against material-induced damage resulting in preserved cell function.

Fabrication and evaluation of porous 2,3-dialdehydecellulose membrane as a potential biodegradable tissue-engineering scaffold

A simple, novel method to produce porous 2,3-dialdehydecellulose (DAC) membranes as a potential tissue-engineering scaffold has been developed from methylolcellulose by the simultaneous water-induced phase separation and sodium chloride salt leaching techniques, followed by oxidation with sodium periodate in water. Membrane pores increased in size with increasing weight or particle size of the sodium chloride salt. The porosity of the membrane was not affected by the salt particle size, but it increased with an increase in the salt weight to 60%. At higher salt weight percentages, no significant change in the membrane porosity was observed. The oxidation step had no effect on the membrane porosity or pore size. All membranes with a porosity value ranging between 87 and 93% showed interconnected porous structures. The use of these membranes as a potential tissue-engineering scaffold was evaluated with the use of human neonatal skin fibroblast cells. Confocal microscopy showed cell attachment and spreading on these membranes. Immunohistochemical tests revealed the presence of collagen type III and fibronectin, indicating that the cells were viable and formed the extracellular matrix. In conclusion, the DAC membrane supports cell adhesion and proliferation and hence shows potential to be used as a tissue-engineering scaffold.

In vivo biocompatibility of bacterial cellulose

The biocompatibility of a scaffold for tissue engineered constructs is essential for the outcome. Bacterial cellulose (BC) consists of completely pure cellulose nanofibrils synthesized by Acetobacter xylinum. BC has high mechanical strength and can be shaped into three-dimensional structures. Cellulose-based materials induce negligible foreign body and inflammatory responses and are considered as biocompatible. The in vivo biocompatibility of BC has never been evaluated systematically. Thus, in the development of tissue engineered constructs with a BC scaffold, it is necessary to evaluate the in vivo biocompatibility. BC was implanted subcutaneously in rats for 1, 4, and 12 weeks. The implants were evaluated in aspects of chronic inflammation, foreign body responses, cell ingrowth, and angiogenesis, using histology, immunohistochemistry, and electron microscopy. There were no macroscopic signs of inflammation around the implants. There were no microscopic signs of inflammation either (i.e., a high number of small cells around the implants or the blood vessels). No fibrotic capsule or giant cells were present. Fibroblasts infiltrated BC, which was well integrated into the host tissue, and did not elicit any chronic inflammatory reactions. The biocompatibility of BC is good and the material has potential to be used as a scaffold in tissue engineering.