几丁糖对大鼠术后腹腔粘连的预防作用

目的　探讨几丁糖对术后腹腔粘连的预防作用。方法　将 45只大鼠随机分为对照组 (A组 ) ,右旋糖酐组 (B组 ) ,几丁糖组 (C组 ) ,于腹腔内浆膜损伤部位分别注入 1%乳酸液 ,3 2 %右旋糖酐 -70液 ,2 %几丁糖乳酸液各 2ml ,术后 14d处死动物 ,观察各组腹腔粘连状况并送病理检查。结果　 3组粘连分级有显著性差异 (P <0 .0 1) ;C组粘连发生率较另 2组为低 ,有显著性差异 (P <0 .0 5 )。光镜下C组炎症反应轻微 ,纤维增生不明显 ;电镜下C组纤维细胞分泌胶原能力弱 ,间皮细胞增生活跃。结论　几丁糖可有效地降低大鼠术后腹腔粘连的发生和粘连程度 ,其作用优于右旋糖酐 -70 ,且不影响切口的愈合。     

Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry

Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of 7 dyne/cm². Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.     

Staphylococcus epidermidis adhesion on modified urea/urethane elastomers

Block urea/urethane co-polymer films present elastomeric properties with the possible tuning of their surface properties within a wide range and are therefore considered relevant surfaces for possible medical applications. In particular, thin free standing films of urea/urethane elastomers with two soft segments, polypropylene oxide and more hydrophobic polybutadiene, develop multi-stable states with surface topography features with remarkable regularity. Moreover, complex surface structures may be obtained by UV radiation treatment followed by suitable mechanical action and also by extraction of the elastomer with a suitable solvent. In the present work, different modified elastomer samples were assayed for Staphylococcus epidermidis adhesion during 2 h and the extent of bacterial adhesion was evaluated by automatic cell enumeration. Bacterial adhesion assays demonstrate that the typical trend relating the increase in the number of adhered bacteria with the increase of the surface roughness does not hold for all materials. Results may be interpreted taking into account both the surface topography and the different types of micro-phase segregation of hydrophobic and hydrophilic parts of the elastomer.     

Surface modification of the polymers present in a polysulfone hollow fiber hemodialyser by covalent binding of heparin or endothelial cell surface heparan sulfate: Flow characteristics and platelet adhesion

The present study addresses the problem of simultaneous surface modification of various polymers, i.e. polysulfone (PSU), polycarbonate (PC), and polyurethane (PU), which constitute the Ultraflux AV 600 S® hollow fibre hemodialyser. An investigation was first made into six different chemical routes aimed at introducing carboxyl groups onto the surface of PSU, PC, and PU model polymers to which heparin (HE) or endothelial cell surface heparan sulfate (ESHS) was covalently bound via the reaction of residual amino groups and a coupling reagent. Carboxyl groups were introduced using three specific reactions based on their nucleophilic or electrophilic introduction into aromatic repeating units of the polymers and three non-specific carboxylation reactions, i.e. UV, heat or redoxactivation via nitrene or radical species. Concentrations of 1-20 nmol COOH groups per cm^-2 led to HE or ESHS surface concentrations corresponding to one or several layers. Two nonspecific carboxylation reactions followed by HE- or ESHS-coupling provided the lowest change in membrane pore structure according to cut off, clearance (urea, phosphate, maltose), ultrafiltration, and diafiltration assessments. In some cases the introduction of excess negatively-charged carboxyl groups and HE improved the flux properties of the modified membranes. The various methods were applied to the dialysis module. Platelet adhesion was not observed in the case of the ESHS-coating of PSU membrane at shear rates of 1050 s^-1, whereas HE and subendothelial matrix showed 56 and 100% coverage, respectively, under similar conditions. The coating of PSU or of other highflux membranes by ESHS appears a promising method for improving membrane properties and to generate biocompatibility characteristics similar to those of natural blood vessels, i.e. inertness to platelet adhesion and no level effects for complement and intrinsic coagulation cascade activation. The ESHS coating may be used without anticoagulants.     

Adsorption of matrix metalloproteinases onto biomedical polymers: a new aspect in biological acceptance

Matrix metalloproteinases (MMPs) are zinc-dependent enzymes involved in the remodelling of connective tissues during the development and wound healing. Moreover, two MMPs, Gelatinase A (MMP-2) and Gelatinase B (MMP-9), are also present in body fluids such as blood and urine and, therefore, they can be in contact with implanted biomaterials and can be adsorbed onto their surface. In order to test this hypothesis disks of different polymers (polystyrene (PS), polyvinyl chloride (PVC), poly(D,L-lactide) (PLA), polymethyl methacrylate (PMMA) and poly(2-hydroxyethyl methacrylate) (PHEMA)) have been exposed to human plasma and adsorbed proteins have been eluted and analyzed. Using Western blot and substrate zymography analysis, we observed that both MMP-2 and MMP-9 adsorbed onto the surfaces of all the polymers, especially hydrophilic ones (PMMA and PHEMA) and PLA, in both the active and inactive forms. Furthermore, we observed that adhesion of human granulocyte neutophils to PMMA, the polymer that adsorbed the higher quantity of MMP-2 and MMP-9 compared to the others, was reduced by more that 50% by the presence of a gelatinase inhibitor. This data suggest a surprising role of these absorbed enzymes in the adhesion of neutrophil onto some polymeric biomaterials surface and, therefore, in the setting of inflammation.     

Synthesis and Characterization of CREKA-Targeted Polymers for the Disruption of Fibrin Gel Matrix Propagation

Recently, efforts to control the propagation of the fibrin gel matrix (FGM) are under investigation as a means of limiting the formation of post-surgical adhesions (PSAs). A series of polymeric biomaterials based on block co-polymers of methacrylic acid (MA) and methoxypolyethylene glycol methacrylate (PEGMA) have been synthesized and characterized in order to study the impact of molecular architecture on the performance of these materials in suppressing FGM development. A robust synthetic strategy has been developed to facilitate the well controlled variation of numerous structural properties, including the relative size of each polymer block, the total polymer length, and the length of poly(ethylene glycol) (PEG) chain length, and to incorporate the fibrin-targeting pentapeptide cysteine–arginine–glutamic acid–lysine–alanine (CREKA). Preliminary investigations, based on quartz crystal microgravimetry (QCM), indicate the importance of molecular architecture in modulating the FGM propagation from model surfaces.     

Plasma-Induced Surface Modification of Polydimethylsiloxane Aimed at Reducing Salt and Protein Deposition

Polydimethylsiloxane (PDMS) is an elastomer that is widely used in construction and for biological and biomedical applications. The biocompatibility of PDMS was improved by different surface treatment methods, i.e., plasma treatment or a combination of plasma treatment with UV-irradiation or redox initiator, to minimize the effects of deposition of salts and proteins. In this work we used the vinyl monomers sulfobetaine and AMPS which have good biocompatible properties.     

Synthesis,Characterization and Drug Release of Biocompatible/Biodegradable Non-toxic Poly(urethane urea)s Based on Poly(ε-caprolactone)s and Lysine-Based Diisocyanate

Segmented poly(urethane urea)s (SPUUs) based on aliphatic diisocyanato (2,6-diisocyanato methyl caproate (lysine-based diisocyanate, LDI)), poly(ε-caprolactone diol)s (PCLs) with molecular weights 530, 1250 and 2000, and 1,4-butanediamine were synthesized in absence of catalyst. The resulting SPUUs, with different soft segment length, were characterized by suitable analytical techniques. The synthesized SPUUs had high molecular weights, low glass-transition temperatures (≤?15°C) and high elongation-at-break. The degradation of SPUUs in alkaline solution and in vitro drug release of sulfamethoxazole in pH 7.4 buffer were investigated. In addition, the degradation behavior of PCL1250-based SPUU was investigated by exposing to a buffer solution and biochemical oxygen demand (BOD) tests in an activated sludge. The drug release data was analyzed by an empirical equation ((M _t/M _∞)=ktⁿ ). Finally, NIH3T3 fibroblasts have been used for cell-adhesion studies on these materials to investigate the biocompatibility. The synthesized SPUUs combine physical and bioresponsive and biodegradable properties that might be employed in wound dressing, drug delivery and tissue-engineering applications.     

Role of Active Oxygen Species and Lipid Peroxidation in Mepirizole-Induced Duodenal Ulcers in Rats

The role of active oxygen species and lipidperoxidation in the pathogenesis of duodenal ulcersinduced by mepirizole was investigated in rats. Oraladministration of mepirizole (200 mg/kg) resulted in ulcer lesions in the proximal duodenum.Thiobarbituric acid-reactive substances (TBA-reactivesubstances), an indicator of lipid peroxidation, alsosignificantly increased in the duodenal mucosa.Myeloperoxidase (MPO) activity in the duodenal mucosa, a signof polymorphonuclear leukocyte (PMN) accumulation,significantly increased. Combination treatment withpolyethylene glycol-modified Serratia Mn-SOD andcatalase significantly decreased the size of the ulcersand TBA-reactive substances in the duodenal mucosa.Allopurinol, a xanthine oxidase inhibitor, also reducedthe size of duodenal ulcers. Both the size of the ulcers and the increase in TBA-reactivesubstances in the duodenal mucosa were significantlylower in PMN-depleted rats. Mepirizole increased thesurface expression of adhesion molecule CD18 on PMNs in vitro. These results suggest that lipidperoxidation, mediated by active oxygen speciesgenerated from xanthine oxidase and PMNs, plays animportant role in the pathogenesis of duodenal ulcersinduced by mepirizole.     

Contact killing antimicrobial acrylic bone cements: preparation and characterization

Novel antimicrobial poly(methyl methacrylate) (PMMA)-based bone cement was synthesized by co-polymerizing PMMA/MMA with various percentages of quaternary amine dimethacrylate (QADMA) by free radical bulk polymerization technique at room temperature using benzoyl peroxide and N, N-dimethyl-p-toulidine (DMPT) as a redox initiator. The modified bone cement was characterized by FT-IR and ¹H-NMR spectral studies. The thermal and physical properties of the bone cements of varying composition of QADMA were evaluated by thermogravimetric analysis (TGA), differential calorimetry (DSC) and contact angle measurements. Peak exothermic temperature was observed to decrease, while setting time increased with increase in QADMA content in the bone cement formulations. The antibacterial activity of the synthesized bone cement containing quaternary amine dimethacrylate against Escherichia coli and Staphylococcus aureus was studied by zone of inhibition, colony count method and scanning electron microscopy (SEM). QADMA containing acrylic bone cement showed a broad spectrum of contact killing antimicrobial properties. Retention of E. coli onto the surface of PMMA bone cement was observed, whereas there was complete prevention of retention of E. coli onto the modified PMMA bone cement with 15% QADMA. The studies were compared with the acrylic bone cement synthesized using 15% N-vinyl-2-pyrrolidone (NVP) in place of QADMA to which iodine was added as an antimicrobial agent during co-polymerization.