Generation of a scaffold free cartilage-like implant from a small amount of starting material

INTRODUCTION: An autologous cellular based treatment of a traumatic cartilage injury requires a procedure whereby a biopsy of healthy cartilage is removed from the patient and the cells isolated and expanded by monolayer passage. This increases the cell number to required levels but also leads to a de-differentiation of the cells. We aim to produce a scaffold-free, de-novo implant from a biopsy of cartilage. METHODS: Bovine chondrocytes were isolated from a small biopsy and expanded. The chondrocytic phenotype of the monolayer expanded cells was recovered during a period of culture in alginate and the effect of factors such as IGF1, TFGbeta1 and dexamethasone was investigated. RESULTS: During the alginate culture period a pre-treatment with IGF1 and dexamethasone was shown to have little effect. IGF1 however increased the glycosaminoglycan/DNA (GAG/DNA) content on day 14 to 84.95+/-5 ng/ng compared with 37.3+/-1.8 ng/ng in the controls (P<0.001). 35S labeling demonstrated an increased GAG synthesis in the presence of IGF1 (P<0.001). IGF1 also induced a increase of DNA content 1383+/-314 ng/bead compared to 512+/-19 ng/bead in the controls (P<0.001).The cells were released from the alginate and cultured in a silicon mould for a further 14 days to obtain a three dimensional implant. Releasing the cells from the alginate and casting in a mould produced an implant of defined shape which contained no foreign material. After 31 days of culture the implants contained 152.4+/-13.14 ng/ng GAG/DNA and 42.93+/-10.23 ng/ng collagen II. DISCUSSION: We believe alginate released chondrocytes provide a real alternative to artificial scaffolds.     

Nano-hydroxyapatite-thermally denatured small intestine sub-mucosa composites for entheses applications

The objective of the present in vitro study was to estimate the adhesion strength of nanometer crystalline hydroxyapatite (HA)-small intestine sub-mucosa (SIS) composites on model implant surfaces. Techniques of thermal denaturation (60 degrees C, 20 min) of SIS were used to enhance the adhesion strength of entheses materials to underlying implants. Specifically, results indicated that the adhesion strength of thermally denatured SIS was 2-3 times higher than that for normal unheated SIS. In addition, aqua-sonicated, hydrothermally treated nano-HA dispersions enhanced the adhesion strength of SIS on implant surfaces. Importantly, results of the present study demonstrated that human skeletal muscle cell (hSkMC) numbers were not affected by thermally denaturing SIS in nano-HA composite coatings; however, they increased on aqua-sonicated nano-HA/SIS composites compared with SIS alone. Interestingly, thermally denatured SIS that contained aqua-sonicated, hydrothermally treated nano-HA decreased human osteoblasts (hOBs) numbers compared with respective unheated composites; all other composites when thermally denatured did not influence hOB numbers. Results also showed that the number of hOBs increased on nano-HA/SIS composites compared with SIS composites alone. Human mesenchymal stem cell (hMSC) numbers were not affected by the presence of nano-HA in SIS composites. For these reasons, the collective results of this in vitro study demonstrated a technique to increase the coating strength of entheses coatings on implant surfaces (using thermally denatured SIS and aqua-sonicated, hydrothermally prepared nano-HA) while, at the same time, supporting cell functions important for entheses regeneration.     

Evaluation of visible implant elastomer as a method for tagging small European eels

Visible implant elastomer (VIE) tagging showed no significant effect on survival of either 230 single-tagged or 60 multiple-tagged small European eels Anguilla anguilla . Mean tag retention was 98·7% during the 5 month laboratory experiments. Multiple VIE tags had no observed effect on European eel locomotor behaviour. VIE appears a reliable method for individually tagging small European eels, and could be useful in capture–recapture field studies.     

Therapeutic potential of neurotrophins for treatment of hearing loss

Degeneration of spiral ganglion neurons (SGNs) and hair cells in the cochlea induced by aging, injury, ototoxic drugs, acoustic trauma, and various diseases is the major cause of hearing loss. Discovery of growth factors that can either prevent SGN and hair-cell death or stimulate hair-cell regeneration would be of great interest. Studies over the past several years have provided evidence that specific neurotrophins are potent survival factors for SGNs and protect these neurons from ototoxic drugs in vitro and in vivo. Current research focuses more on understanding the mechanism of hair-cell regeneration/differentiation and identification of growth factors that can stimulate hair-cell regeneration. SGNs are required to relay the signal to the central nervous system even when a cochlear implant is used to replace hair-cell function or in the case that cochlear sensory epithelium can be stimulated to regenerate new hair cells successfully. Therefore, neurotrophins may have their therapeutic value in prevention and treatment of hearing impairment.     

Selective protein transport through a thin cellulose coated porous membrane

A new composite membrane was designed and studied for permselectivity of various molecular weight proteins. The membrane is composed of a porous substrate membrane [Durapore; poly(vinylidene fluoride)] coated with a thin dense layer of regenerated cellulose. This composite membrane was fabricated by spin coating a cellulose acetate solution onto the membrane, followed by alkaline hydrolysis of the cellulose acetate coating to regenerate cellulose. The coated layer was physically characterized by scanning electron microscopy (SEM) and infrared (IR) spectroscopy. In addition, the water uptake into and permeation properties of macromolecules across the coated and uncoated membranes were studied. A typical composite membrane coating was 0.8 +/- 0.2 mum thick, resulting in a molecular weight cutoff of approximately 40,000 daltons. This composite membrane also demonstrated negligible diffusional lag time for permeants, due to the diffusional barrier. (c) 1994 John Wiley & Sons, Inc.     

Age-related satisfaction with complete dentures,desire for improvement and attitudes to implant treatment

In the edentulous lower jaw implant stabilised dentures have proved clinically so successful that the indication for this treatment is now being discussed more often with geriatric patients. The aim of this study of edentate subjects was to determine the age-relation of the demand for denture improvement, the risks and feasibility of implant treatment. Sixty four complete denture wearers aged from 42 to 84 years took part in the study. A questionnaire was used to determine the subjective demand for denture improvement. For 33 subjects implants seemed possible. For these patients fear and scepticism concerning implant treatment were specified and quantified. Impaired general health was the most frequent absolute contra-indication for implants; the local oral prerequisites tended to be slightly less favourable in elderly. Older patients were more satisfied with poorly fitting dentures and were less prepared to take trouble to achieve denture improvement. Although scepticism concerning implant treatment was not age-related, patients who were keen for an improvement of their dentures were significantly younger and less sceptical about implants.     

Aptamer-based capture molecules as a novel coating strategy to promote cell adhesion

The improvement of the cytocompatibility of medical implants is a major goal in biomaterials research. During the last years many researchers worked on the fascinating approach to seed the respective cell types on various artificial substrates before implantation. For instance, cell-seeded implants are supposed to be better candidates for transplantable bone substitutes than conventional artificial bone grafts. To improve cell seeding efficiency and cytocompatibility, we designed a new coating material for medical implants. We used aptamers, highly specific cell binding nucleic acids generated by combinatorial chemistry with an in vitro selection called systematic evolution of exponential enrichment (SELEX). Aptamers do have high binding affinity and selectivity to their target. In our study, human osteoblasts from osteosarcoma tissue were used as a target to create the aptamer. Single aptamer mediated cell sorting assays showed the binding affinity with osteoblasts. Additionally, the aptamers immobilized on tissue culture plates could capture osteoblasts directly and rapidly from the cell solution. This model proves that aptamer coated artificial surfaces can greatly enhance cell adhesion. We assume that this strategy is capable to improve the clinical application of tissue engineered implants.     

A time-dependent healing function for immediate loaded implants

Current interest in immediate dental implant loading has grown due to a number of clinical advantages this treatment modality offers. To obtain a deeper insight into the changing mechanical properties during the healing phase, results from removal torque tests are used in a biomechanical model. The ultimate removal torques, which depend on healing time, are described by a time-dependent healing function. The bone behavior is modeled using an elastic law with damage. The evolution of damage is represented with an incremental equation with an initial damage value and two material parameters. The nonlinear relationship between the torque and the angle of rotation up to the ultimate torque can be calculated. By changing the elastic parameter in the elastic damage law, the remodeling process can be characterized. In a further step, the elastic parameters and the limits for shear stress from the biomechanical model for the removal torque will be used in an FE analysis in order to obtain information on the axial loading limits of a dental implant at different healing times.     

The effect of L-NAME administrations after oral mucosal incision on wound NO level in rabbit

The aim of the current study was to comparatively investigate the effect of inhibition of nitric oxide (NO) production by N-nitro-L-arginine methyl ester (L-NAME), an isoform non-specific inhibitor of nitric oxide synthase (NOS), after oral mucosal incision on wound tissue NO levels. A standard incision was applied to the oral mucosa of rabbits. After oral mucosal incision, rabbits were divided into five groups as follows: (1) Untreated incisional group (control); (2) Titanium (Ti) implanted group; (3) Ti + Polyethylene glycol (PEG) 4000 implanted group; (4) Ti + PEG 4000 + L-NAME (2 × 10⁻⁴ M) implanted group and (5) i.p. L-NAME administrated group (10 mg/kg). At 5 days after oral incision operations, wound tissue strips and plasma were obtained from rabbits. Oral wound tissue and plasma nitric oxide, plasma thiobarbituric acid reactive substances (TBARS) and total sulfhydryl group (RSH) levels were investigated. Plasma TBARS and NOx levels decreased after i.p. L-NAME administration. Total RSH group levels were not changed in all groups (p>0.05). This means that L-NAME inhibits the deteriorating effects of free radicals without affecting healing. L-NAME in PEG and titanium also has no effect on tissue and plasma NOx levels. These findings indicate that NO generation will not be affected both Ti and local nitric oxide synthase (NOS) inhibitor. (Mol Cell Biochem 278: 65–69, 2005)     

抗生物被膜类医用植入材料的未来发展展望

生物被膜极大提高了微生物本身的耐药性(比浮游态细菌高1000-倍)和对环境的适应能力(温度、压强、氧化剂、以及p H),而另一方面医用材料本身会导致异物入侵造成的机体免疫力下降。因而,生物被膜给医用材料植入带来了更大的感染风险,也推动了医用抑菌材料的不断改进和发展。对医用材料中微生物组成的研究以及生物被膜形成机理的逐步揭示成为了抑菌材料发展的导向。抑菌材料的改性主要通过更换材质和形成涂层等方式来改变材料表面的物化性质,其中涂层法是目前被大量尝试的热点。本文简要介绍了医药材料在安全性方面面临的问题以及生物被膜理论研究的主要成果,并详细讨论了抗生素、抑菌金属离子、氧化剂、群体感应淬灭分子、酶等被尝试用于材料涂层抑制生物被膜形成的原理、实例、以及优劣。最后,本文对未来抗生物被膜类抑菌材料的发展趋势进行了展望。