Synthesis, physiochemical characterization, and biocompatibility of a chitosan/dextran-based hydrogel for postsurgical adhesion prevention

Characterization of an Injectable Chitosan Hydrogel for the Tunable, Localized Delivery of Immunotherapeutics

Localized delivery of immunotherapeutics within a tumor has the potential to reduce systemic toxicities and improve treatment outcomes in cancer patients. Unfortunately, local retention of therapeutics following intratumoral injection is problematic and is insufficiently considered. Dense tumor architectures and high interstitial pressures rapidly exclude injections of saline and other low-viscosity solutions. Hydrogel-based delivery systems, on the other hand, can resist shear forces that cause tumor leakage and thus stand to improve the local retention of coformulated therapeutics. The goal of the present work was to construct a novel, injectable hydrogel that could be tuned for localized immunotherapy delivery. A chitosan-based hydrogel, called XCSgel, was developed and subsequently characterized. Nuclear magnetic resonance studies were performed to describe the chemical properties of the new entity, while cryo-scanning electron microscopy allowed for visualization of the hydrogel's cross-linked network. Rheology experiments demonstrated that XCSgel was shear-thinning and self-healing. Biocompatibility studies, both in vitro and in vivo, showed that XCSgel was nontoxic and induced transient mild-to-moderate inflammation. Release studies revealed that coformulated immunotherapeutics were released over days to weeks in a charge-dependent manner. Overall, XCSgel displayed several clinically important features, including injectability, biocompatibility, and imageability. Furthermore, the properties of XCSgel could also be controlled to tune the release of coformulated immunotherapeutics.

[Fundamentals and practice of the application of nasal packing in sinonasal surgery]

BACKGROUND AND OBJECTIVES

This paper presents an overview on nasal packing materials which are available in Germany. The current literature is analyzed whether there are robust criteria regarding use nasal packing after sinonasal surgery, whether there are fundamental and proven advantages or disadvantages of products, and what this means in clinical practice.

MATERIALS AND METHODS

Selective literature analysis using the PubMed database (key words "nasal packing", "nasal tamponade", "nasal surgery", "sinonasal surgery", or "sinus surgery"), corresponding text books and resulting secondary literature.

RESULTS AND CONCLUSIONS

Because of systematic methodological shortcomings, the literature does not help in the decision-making about which nasal packing should be used after which kind of sinonasal surgery. In fact, individual approaches for the many different clinical scenarios are recommended. In principle, nasal packing aims in hemostasis, should promote wound healing, and should not result in secondary morbidity. Nasal packing materials should be smooth (non-absorbable materials), inert (absorbable materials), and should not exert excessive pressure. Using non-absorbable packing entails the risk of potentially lethal aspiration and ingestion. For safety reasons inpatient control is recommended as long as this packing is in situ. With other, uncritical packing materials and in patients with special conditions, outpatient control could be justified.

Dextran-Based Injectable Hydrogel Composites for Bone Regeneration

Currently, bone infections caused by diseases or injuries are a major health issue. In addition, the conventional therapeutic approaches used to treat bone diseases or injuries present several drawbacks. In the area of tissue engineering, researchers have been developing new alternative therapeutic approaches, such as scaffolds, to promote the regeneration of injured tissues. Despite the advantages of these materials, most of them require an invasive surgical procedure. To overcome these problems, the main focus of this work was to develop scaffolds for bone regeneration, which can be applied using injectable hydrogels that circumvent the use of invasive procedures, while allowing for bone regeneration. Throughout this work, injectable hydrogels were developed based on a natural polymer, dextran, along with the use of two inorganic compounds, calcium β-triphosphate and nanohydroxyapatite, that aimed to reinforce the mechanical properties of the 3D mesh. The materials were chemically characterized considering the requirements for the intended application: the swelling capacity was evaluated, the degradation rate in a simulated physiological environment was assessed, and compression tests were performed. Furthermore, vancomycin was incorporated into the polymeric matrices to obtain scaffolds with antibacterial performance, and their drug release profile was assessed. The cytotoxic profile of the hydrogels was assessed by an MTS assay, using osteoblasts as model cells. The data obtained demonstrated that dextran-based hydrogels were successfully synthesized, with a drug release profile with an initial burst between 50 and 80% of the drug. The hydrogels possess fair biocompatibility. The swelling capacity showed that the stability of the samples and their degradation profile is compatible with the average time period required for bone regeneration (usually about one month) and have a favorable Young's modulus (200-300 kPa). The obtained hydrogels are well-suited for bone regeneration applications such as infections that occur during implantation or bone graft substitutes with antibiotics.

Preparation of injectable hydrophilic dextran/AgNPs nanocomposite product: White light active biomolecules as an antitumor agent

Incidence of various cancers including melanoma continues to rise worldwide. While treatment options have expanded in the recent years, the benefit of these treatments suffer from short period of duration for many patients. Hence, new treatment options are highly desired. Here, we propose a method combining a Dextran/reactive-copolymer/AgNPs nanocomposite and a harmless visible light approach to obtain a plasma substitute carbohydrate-based nanoproduct (D@AgNP) that shows strong antitumor activity. Light-driven polysaccharide-based nanocomposite provided essential conditions for extra small (8-12nm) AgNPs capping with subsequent specific self-assembly into spherical-like cloud nanostructures. Obtained biocompatible D@AgNP are stable over six months at room temperature and demonstrated absorbance peak at 406 nm. New formulated nanoproduct revealed efficient anticancer properties against A375 with IC50 0.0035 mg/mL following 24-h incubation; complete cell death is achieved at 0.001 mg/mL and 0.0005 mg/mL by 24- and 48-h time points, respectively. SEM examination shows that D@AgNP altered the shape of the cell structure and damaged the cell membrane. TEM finding shows that D@AgNP are mostly localized at vesicles such as the endosomes, lysosomes and mitochondria. It is anticipated that the introduced new method serves as the cornerstone for improving the generation of biocompatible hydrophilic carbohydrate-based anticancer drugs.

Detailed Structural Characterization of Oxidized Sucrose and Its Application in the Fully Carbohydrate-Based Preparation of a Hydrogel from Carboxymethyl Chitosan

Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed by applying various nuclear magnetic resonance techniques, which permitted the structural and quantitative characterization of the two main OS products, each of which contained four aldehyde groups. In addition, we investigated the use of OS as a cross-linking agent in the preparation of a hydrogel from carboxymethyl chitosan (CMC), one of the most popular polysaccharides for use in biomedical applications. The primary amine groups of CMC were immediately cross-linked with the aldehyde groups of OS to form hydrogels without the requirement for a catalyst. It was found that the degree of cross-linking could be easily controlled by the feed amount of OS during CMC hydrogel preparation and the final cross-linking degree affected the thermal, swelling, and rheological properties of the obtained hydrogel. The results presented in this study are therefore expected to be applicable in the preparation of fully carbohydrate-based hydrogels for medical and pharmaceutical applications.

Dynamic and Self-Healable Chitosan/Hyaluronic Acid-Based In Situ-Forming Hydrogels

In situ-forming, biodegradable, and self-healing hydrogels, which maintain their integrity after damage, owing to dynamic interactions, are essential biomaterials for bioapplications, such as tissue engineering and drug delivery. This work aims to develop in situ, biodegradable and self-healable hydrogels based on dynamic covalent bonds between N-succinyl chitosan (S-CHI) and oxidized aldehyde hyaluronic acid (A-HA). A robust effect of the molar ratio of both S-CHI and A-HA was observed on the swelling, mechanical stability, rheological properties and biodegradation kinetics of these hydrogels, being the stoichiometric ratio that which leads to the lowest swelling factor (×12), highest compression modulus (1.1·10−3 MPa), and slowest degradation (9 days). Besides, a rapid (3 s) self-repairing ability was demonstrated in the macro scale as well as by rheology and mechanical tests. Finally, the potential of these biomaterials was evidenced by cytotoxicity essay (>85%).

Aqueous Modification of Chitosan with Itaconic Acid to Produce Strong Oxygen Barrier Film

In this study, the chemical modification of chitosan using itaconic acid as a natural-based unsaturated dicarboxylic acid was investigated. In an aqueous environment, the amine group of chitosan reacts with itaconic acid to produce a chitosan derivative with pyrrolidone-4-carboxylic acid group. On the basis of the elemental analysis, 15% of the amine groups of chitosan reacted, thus creating modified chitosan with amine and carboxylic acid functionalities. Due to the presence of amine and carboxylic acid groups, the surface charge properties of the chitosan were notably altered after itaconic acid modification. In an aqueous solution, the modified chitosan exhibited zwitterionic properties, being cationic at low pH and turning anionic when the pH was increased over 6.5, whereas the original chitosan remained cationic until pH 9. Furthermore, it was demostrated that the modified chitosan was suitable for the preparation of a self-standing film with similarly high transparency but notably higher mechanical strength and oxygen barrier properties compared to a film made from the original chitosan. In addition, the thermal stability of the modified chitosan film was higher than that of the original chitosan film, and the modified chitosan exhibited flame-retardant properties.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

Prevention of adhesions post-abdominal surgery: Assessing the safety and efficacy of Chitogel with Deferiprone in a rat model

Introduction

Adhesions are often considered to be an inevitable consequence of abdominal and pelvic surgery, jeopardizing the medium and long-term success of these procedures. Numerous strategies have been tested to reduce adhesion formation, however, to date, no surgical or medical therapeutic approaches have been successful in its prevention. This study demonstrates the safety and efficacy of Chitogel with Deferiprone and/or antibacterial Gallium Protoporphyrin in different concentrations in preventing adhesion formation after abdominal surgery.

Materials and methods

112 adult (8–10 week old) male Wistar albino rats were subjected to midline laparotomy and caecal abrasion, with 48 rats having an additional enterotomy and suturing. Kaolin (0.005g/ml) was applied to further accelerate adhesion formation. The abrasion model rats were randomized to receive saline, Chitogel, or Chitogel plus Deferiprone (5, 10 or 20 mM), together with Gallium Protoporphyrin (250μg/mL). The abrasion with enterotomy rats were randomised to receive saline, Chitogel or Chitogel with Deferiprone (1 or 5 mM). At day 21, rats were euthanised, and adhesions graded macroscopically and microscopically; the tensile strength of the repaired caecum was determined by an investigator blinded to the treatment groups.

Results

Chitogel with Deferiprone 5 mM significantly reduced adhesion formation (p<0.01) when pathologically assessed in a rat abrasion model. Chitogel with Deferiprone 5 mM and 1 mM also significantly reduced adhesions (p<0.05) after abrasion with enterotomy. Def-Chitogel 1mM treatment did not weaken the enterotomy site with treated sites having significantly better tensile strength compared to control saline treated enterotomy rats.

Conclusions

Chitogel with Deferiprone 1 mM constitutes an effective preventative anti-adhesion barrier after abdominal surgery in a rat model. Moreover, this therapeutic combination of agents is safe and does not weaken the healing of the sutured enterotomy site.

Peptide Chitosan/Dextran Core/Shell Vascularized 3D Constructs for Wound Healing

Three-dimensional (3D) bioprinting has emerged to create novel cell-based therapies for regenerative medicine applications. Vascularized networks within engineered constructs are required, and toward this end, we report a promising strategy using core-shell (c/s) extrusion 3D-bioprinting technology that employs biomimetic biomaterials to construct regenerative, prevascularized scaffolds for wound care. A custom-designed cell-responsive bioink consisting of a 13% (w/v) cell-laden gelatin methacryloyl (GelMA) shell surrounding a peptide-functionalized, succinylated chitosan (C)/dextran aldehyde (D) cell-laden core was successfully bioprinted resulting in organized microdesigns exhibiting excellent cell viability and subsequent vessel formation. Our templating strategy takes advantage of GelMA's intrinsic thermoreversible properties of low degree of acryloyl functionalization used in combination with a lightly, chemically cross-linked peptide-CD core to serve as temporal structural supports that stabilize during extrusion onto a cooled platform. Mechanical integrity was further strengthened layer-by-layer via GelMA UV photo-cross-linking. We report the first example of GelMA used in combination with a peptide-CD bioink to c/s 3D-bioprint regenerative, prevascularized constructs for wound care. Particular cell adhesion and proteolytic peptide-CD functionalized pair combinations, P15/MMP-2 and P15/cRGD, were found to significantly increase growth of human bone-marrow-derived mesenchymal stems cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs). The constructs delivered two cell types: hBMSCs in the shell bioink and HUVECs within the core bioink. Cord-like, natural microvascularization was shown with endothelial cell marker expression as confirmed by immunofluorescence (IF) staining exhibiting tubelike structures. In addition, in vitro skin wound healing activity of the construct showed a ∼twofold rate of wound closure. Overall, c/s 3D-bioprinted, peptide-CD/GelMA constructs provided the appropriate microenvironment for in vitro stem and endothelial cell viability, delivery, and differentiation. We foresee these custom constructs as representing a fundamental step toward engineering larger scale regenerative, prevascularized tissues.

Complexes of glucose oxidase with chitosan and dextran possessing enhanced stability

In this study, the different mole ratios of glucose oxidase/chitosan/dextran-aldehyde and glucose oxidase/chitosan/dextran-sulfate complexes were synthesized. The modification of glucose oxidase by non-covalent complexation with dextran and chitosan in different molar ratios was studied in order to increase the enzyme activity. The enzyme/polymer complexes obtained were investigated by UV spectrophotometer and dynamic light scattering. Activity determination of synthesized complexes and free enzyme were performed at a temperature range. The best results were obtained by C_chitosan/C_{dextran-aldehyde} = 10/1 ratio and C_chitosan/C_{dextran-sulfate} = 1/5 ratio that were used in thermal stability, shelf life, salt stress, and ethanol effect experiments. The results demonstrated that both complexes were thermally stable at 60 °C and had superior storage stability compared to the free glucose oxidase. Complexes showed higher enzymatic activity than free enzyme in the organic solvent environment using 10% ethanol. The complexes were resistant to salt stress containing 0.1 M NaCl or CaCl₂. The particle size distribution results of the triple complex evaluated the complexation of the chitosan, dextran derivative, and glucose oxidase. The average size of the triple complex in diameter was found to be 325.8 ± 9.3 nm. Overall findings suggest that the complexes of glucose oxidase, chitosan, and dextran showed significant enhancement in the enzyme activity.

Effect of a poloxamer-based thermosensitive gel on rotator cuff repair in a rabbit model: a controlled laboratory study

BACKGROUND

A common complication after rotator cuff repair is postoperative stiffness, which can be reduced by a simple application of an anti-adhesive agent. However, anti-adhesive agents may affect rotator cuff healing by preventing fibrosis. This experimental animal study evaluated the effect of the application of a poloxamer-based thermosensitive anti-adhesive gel and its influence on the healing of an acute rotator cuff repair in a rabbit model.

METHODS

Acute rotator cuff repair (supraspinatus tendon) was performed using a transosseous suturing method. One shoulder on a randomly selected side was treated with a local application of the anti-adhesive agent (applied side), and saline was applied to the contralateral side (control side). Biomechanical testing and histological analyses were performed at 4 and 8 weeks postoperatively. Eight rabbits were included for each testing and time point, for a total of 32 rabbits.

RESULTS

The failure load at 4 weeks was lower in the experimental group (95.2 ± 19.6 N vs. 110.0 ± 20.5 N; P = 0.017). Conversely, at 8 weeks, the failure load was higher in the experimental group (148.3 ± 16.2 N) than in the control group (122.4 ± 16.9 N; P = 0.002). Histological analyses revealed no statistically significant differences in the tendon maturing scores at 4 and 8 weeks between the two groups (all P > 0.05). The thickness of the fibrosis between the rotator cuff tendon and deltoid was thinner in the experimental group at both time points (0.50 ± 0.25 vs. 1.27 ± 0.47; P = 0.002 at 4 weeks, and 0.37 ± 0.35 vs. 1.39 ± 0.50; P = 0.003 at 8 weeks).

CONCLUSIONS

Application of an anti-adhesive agent in this rotator cuff model confirmed the agent's effectiveness at reducing fibrosis in the subacromial space. The healing of the tendon showed interesting results, as the experimental group had poorer biomechanical strength at 4 weeks but superior strength at 8 weeks.

TiO2 as Photosensitizer and Photoinitiator for Synthesis of Photoactive TiO2-PEGDA Hydrogel Without Organic Photoinitiator

The replacement of potentially toxic photoinitiators is of increasing interest regarding the synthesis of biomaterials by photopolymerization. Therefore, we present a new method for the preparation of UV polymerized hydrogels with TiO2 as a photoinitiator. Titania is known to be an excellent photoactive compound which is non-toxic, inert, and cheap. The so-formed hydrogels possess excellent mechanical properties, a high swelling ratio, and high thermal stability. Furthermore, no TiO2 is released from the hydrogels. Thus, the material is highly suitable for medical applications. Additionally, the present TiO2 in the hydrogels remains photoactive as demonstrated by degradation of methylene blue. This enables the application of TiO2-hydrogels in photodynamic therapy.

Bioadhesives for internal medical applications: A review

Bioadhesives such as tissue adhesives, hemostatic agents, and tissue sealants have gained increasing popularity in different areas of clinical operations during the last three decades. Bioadhesives can be categorized into internal and external ones according to their application conditions. External bioadhesives are generally applied in topical medications such as wound closure and epidermal grafting. Internal bioadhesives are mainly used in intracorporal conditions with direct contact to internal environment including tissues, organs and body fluids, such as chronic organ leak repair and bleeding complication reduction. This review focuses on internal bioadhesives that, in contrast with external bioadhesives, emphasize much more on biocompatibility and adhesive ability to wet surfaces rather than on gluing time and intensity. The crosslinking mechanisms of present internal bioadhesives can be generally classified as follows: 1) chemical conjugation between reactive groups; 2) free radical polymerization by light or redox initiation; 3) biological or biochemical coupling with specificity; and 4) biomimetic adhesion inspired from natural phenomena. In this review, bioadhesive products of each class are summarized and discussed by comparing their designs, features, and applications as well as their prospects for future development.

STATEMENT OF SIGNIFICANCE

Despite the emergence of numerous novel bioadhesive formulations in recent years, thus far, the classification of internal and external bioadhesives has not been well defined and universally acknowledged. Many of the formulations have been proposed for treatment of several diseases even though they are not applicable for such conditions. This is because of the lack of a systematic standard or evaluation protocol during the development of a new adhesive product. In this review, the definition of internal and external bioadhesives is given for the first time, and with a focus on internal bioadhesives, the criteria of an ideal internal bioadhesive are adequately discussed; this is followed by the review of recently developed internal bioadhesives based on different gluing mechanisms.

Transparent Low Molecular Weight Poly(Ethylene Glycol) Diacrylate-Based Hydrogels as Film Media for Photoswitchable Drugs

Hydrogels have shown a great potential as materials for drug delivery systems thanks to their usually excellent bio-compatibility and their ability to trap water-soluble organic molecules in a porous network. In this study, poly(ethylene glycol)-based hydrogels containing a model dye were synthesized by ultraviolet (UV-A) photopolymerization of low-molecular weight macro-monomers and the material properties (dye release ability, transparency, morphology, and polymerization kinetics) were studied. Real-time infrared measurements revealed that the photopolymerization of the materials was strongly limited when the dye was added to the uncured formulation. Consequently, the procedure was adapted to allow for the formation of sufficiently cured gels that are able to capture and later on to release dye molecules in phosphate-buffered saline solution within a few hours. Due to the transparency of the materials in the 400⁻800 nm range, the hydrogels are suitable for the loading and excitation of photoactive molecules. These can be uptaken by and released from the polymer matrix. Therefore, such materials may find applications as cheap and tailored materials in photodynamic therapy (i.e., light-induced treatment of skin infections by bacteria, fungi, and viruses using photoactive drugs).

In situ cross-linking carbodiimide-modified chitosan hydrogel for postoperative adhesion prevention in a rat model

BACKGROUND

Postoperative intra-abdominal adhesion often causes many complications. Chitosan fluid has been used in clinic to prevent intra-abdominal adhesion. However, fluid can be easily diluted and cannot stay on the wound site. As hydrogel is able to form stable physical barrier to separate injured tissues, we developed a chitosan hydrogel for better prevention of intra-abdominal adhesion in this study.

METHODS

We synthesized a carbodiimide-derivatized chitosan gelatin (cd-CS-gelatin) hydrogel and investigated its rheological properties. A rat model was used to compare the anti-adhesion effect of chitosan hydrogel and fluid. The wounds were created with damage of the underlying muscle of the abdominal wall and the serosal layer of the cecum. They were coated with chitosan fluid or cd-CS-gelatin hydrogel. At day 14 after surgery, the animals were euthanized and intra-abdominal adhesion was assessed.

RESULTS

The cd-CS-gelatin hydrogel solidified within 3min after the mixing of the reagents. The cecum-abdomen adhesion occurred in all rats without anti-adhesion treatment. The application of cd-CS-gelatin significantly reduced the adhesion rate from 100% to 50%, compared the chitosan fluid only to 88%. The decrease of adhesion breaking strength also manifested that cd-CS-gelatin was more effective than chitosan fluid to reduce postsurgical intra-abdominal adhesion formation.

CONCLUSIONS

Chitosan hydrogel is more effective than chitosan fluid to prevent postoperative cecum-abdomen adhesion. It indicates that hydrogel could be a more promising state than liquid to prevent postoperative intra-abdominal adhesion.

A Topical Hydrogel with Deferiprone and Gallium-Protoporphyrin Targets Bacterial Iron Metabolism and Has Antibiofilm Activity

Many infectious diseases are associated with multidrug-resistant (MDR) bacteria residing in biofilms that require high antibiotic concentrations. While oral drug delivery is frequently ineffective, topical treatments have the potential to deliver higher drug concentrations to the infection site while reducing systemic side effects. This study determined the antibiofilm activity of a surgical wound gel loaded with the iron chelator deferiprone (Def) and the heme analogue gallium-protoporphyrin (GaPP), alone and in combination with ciprofloxacin. Activity against MDR Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Acinetobacter johnsonii biofilms was assessed in the colony biofilm and artificial wound model by enumeration of CFU and correlative light/electron microscopy. While Staphylococcus biofilms were equally susceptible to GaPP and Def-GaPP gels (log10 reduction of 3.8 and 3.7, respectively), the Def-GaPP combination was crucial for significant activity against P. aeruginosa biofilms (log10 reduction of 1.3 for GaPP and 3.3 for Def-GaPP). When Def-GaPP gel was combined with ciprofloxacin, the efficacy exceeded the activity of the individual compounds. Def-GaPP delivered in a surgical wound gel showed significant antibiofilm activity against different MDR strains and could enhance the gel's wound-healing properties. Moreover, Def-GaPP indicated a potentiation of ciprofloxacin. This antibiofilm strategy has potential for clinical utilization as a therapy for topical biofilm-related infections.

Design and development of polysaccharide hemostatic materials and their hemostatic mechanism

The formation of stable blood clots or hemostasis is essential to prevent major blood loss and death from excessive bleeding.

Safety and Efficacy of Chitosan-Dextran Hydrogel in the Middle Ear in an Animal Model

OBJECTIVES

To investigate the efficacy of chitosan-dextran hydrogel (CDH) in preventing postoperative adhesions between the tympanic membrane (TM) and intratympanic structures, and to evaluate its ototoxicity in an animal study.

METHODS

In the first step, ototoxicity was evaluated with 7 male albino guinea pigs (GPs) via auditory brainstem responses (ABR) before and 4 weeks after unilateral intratympanic injection of CDH and saline solution contralaterally. In the second step, 12 GPs underwent bilateral ear surgery. The middle ear (ME) mucosa was abraded, and the cavity was filled with CDH on one side and packed with Gelfoam on the contralateral side. A control group of 6 GPs underwent the same procedure except that no material was applied in the ME. The animals were euthanized at the end of the 7th week, and otomicroscopic findings were noted and the temporal bones harvested for the histologic examination. The findings were scored and compared.

RESULTS

There was no statistically significant difference between the pre- and postoperative ABR thresholds. In the otomicroscopic findings, the most prominent difference between the two groups was the presence of retraction of the TM in the Gelfoam group. The histopathologic findings revealed a higher degree of inflammation in the Gelfoam group compared with the CDH group.

CONCLUSION

This study demonstrated that CDH has no ototoxic effects in GPs. Its use as an ME packing material revealed significantly less TM retraction and inflammatory reaction compared with Gelfoam.

Comprehensive review on endonasal endoscopic sinus surgery

Endonasal endoscopic sinus surgery is the standard procedure for surgery of most paranasal sinus diseases. Appropriate frame conditions provided, the respective procedures are safe and successful. These prerequisites encompass appropriate technical equipment, anatomical oriented surgical technique, proper patient selection, and individually adapted extent of surgery. The range of endonasal sinus operations has dramatically increased during the last 20 years and reaches from partial uncinectomy to pansinus surgery with extended surgery of the frontal (Draf type III), maxillary (grade 3-4, medial maxillectomy, prelacrimal approach) and sphenoid sinus. In addition there are operations outside and beyond the paranasal sinuses. The development of surgical technique is still constantly evolving. This article gives a comprehensive review on the most recent state of the art in endoscopic sinus surgery according to the literature with the following aspects: principles and fundamentals, surgical techniques, indications, outcome, postoperative care, nasal packing and stents, technical equipment.

Effects of different forms of chitosan on intercellular junctions of mouse fibroblasts in vitro

Chitosan is a linear polysaccharide that has many biomedical applications. We compared the effects of chitosan, in both solution and membranous form, on intercellular adhesion of Swiss 3T3 mouse fibroblasts. Cells were grown as spheroidal cell cultures. Some control cell spheroids were cultured without chitosan and two experimental groups were cultured with chitosan. Chitosan in solution was used for one experimental group and chitosan in membranous form was used for the other. For each group, intercellular adhesion was investigated on days 5 and 10 of culture. Transmission electron microscopy revealed well-defined cellular projections that were more prominent in cells exposed to either membranous or solution forms of chitosan than to the chitosan-free control. Immunocytochemical staining of ICAM-1 and e-cadherin was used to determine the development of intercellular junctions. Compared to the weakly stained control, strong reactions were observed in both chitosan exposed groups at both 5 and 10 days. Cells were treated with 5-bromo-2-deoxyuridine (BrdU) and incubated with anti-BrdU primary antibody to assess proliferation. Both the solution and membranous forms of chitosan increased proliferation at both 5 and 10 days. Cellular viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The MTT assay indicated high cell viability; maximum viability was obtained with the solution form of chitosan at day 5. Chitosan exposure increased the number of intercellular junctions and showed a significant proliferative effect on 3T3 mouse fibroblasts.

Reducing the Oxidation Level of Dextran Aldehyde in a Chitosan/Dextran-Based Surgical Hydrogel Increases Biocompatibility and Decreases Antimicrobial Efficacy

A highly oxidized form of a chitosan/dextran-based hydrogel (CD-100) containing 80% oxidized dextran aldehyde (DA-100) was developed as a post-operative aid, and found to significantly prevent adhesion formation in endoscopic sinus surgery (ESS). However, the CD-100 hydrogel showed moderate in vitro cytotoxicity to mammalian cell lines, with the DA-100 found to be the cytotoxic component. In order to extend the use of the hydrogel to abdominal surgeries, reformulation using a lower oxidized DA (DA-25) was pursued. The aim of the present study was to compare the antimicrobial efficacy, in vitro biocompatibility and wound healing capacity of the highly oxidized CD-100 hydrogel with the CD-25 hydrogel. Antimicrobial studies were performed against a range of clinically relevant abdominal microorganisms using the micro-broth dilution method. Biocompatibility testing using human dermal fibroblasts was assessed via a tetrazolium reduction assay (MTT) and a wound healing model. In contrast to the original DA-100 formulation, DA-25 was found to be non-cytotoxic, and showed no overall impairment of cell migration, with wound closure occurring at 72 h. However, the lower oxidation level negatively affected the antimicrobial efficacy of the hydrogel (CD-25). Although the CD-25 hydrogel's antimicrobial efficacy and anti-fibroblast activity is decreased when compared to the original CD-100 hydrogel formulation, previous in vivo studies show that the CD-25 hydrogel remains an effective, biocompatible barrier agent in the prevention of postoperative adhesions.