A Bioinspired Gelatin-Amorphous Calcium Phosphate Coating on Titanium Implant for Bone Regeneration

Biocompatible and bio-active coatings can enhance and accelerate osseointegration via chemical binding onto substrates. Amorphous calcium phosphate (ACP) has been shown as a precursor to achieve mineralization in vertebrates and invertebrates under the control of biological macromolecules. This work presents a simple bioinspired Gelatin-CaPO4 (Gel-CaP) composite coating on titanium surfaces to improve osseointegration. The covalently bound Gel-CaP composite is characterized as an ACP-Gel compound via SEM, FT-IR, XRD, and HR-TEM. The amorphous compound coating exhibits a nanometer range thickness and improved elastic modulus, good wettability, and nanometric roughness. The amount of grafted carboxyl groups and theoretical thickness of the coatings are also investigated. More importantly, MC3T3 cells, an osteoblast cell line, show excellent cell proliferation and adhesion on the Gel-CaP coating. The level of osteogenic genes is considerably upregulated on Ti with Gel-CaP coatings compared to uncoated Ti, demonstrating that Gel-CaP coatings possess a unique osteogenic ability. To conclude, this work offers a new perspective on functional, bioactive titanium coatings, and Gel-CaP composites can be a low-cost and promising candidate in bone regeneration.

Formation of Amorphous Iron-Calcium Phosphate with High Stability

Amorphous iron-calcium phosphate (Fe-ACP) plays a vital role in the mechanical properties of teeth of some rodents, which are very hard, but its formation process and synthetic route remain unknown. Here, the synthesis and characterization of an iron-bearing amorphous calcium phosphate in the presence of ammonium iron citrate (AIC) are reported. The iron is distributed homogeneously on the nanometer scale in the resulting particles. The prepared Fe-ACP particles can be highly stable in aqueous media, including water, simulated body fluid, and acetate buffer solution (pH 4). In vitro study demonstrates that these particles have good biocompatibility and osteogenic properties. Subsequently, Spark Plasma Sintering (SPS) is utilized to consolidate the initial Fe-ACP powders. The results show that the hardness of the ceramics increases with the increase of iron content, but an excess of iron leads to a rapid decline in hardness. Calcium iron phosphate ceramics with a hardness of 4 GPa can be achieved, which is higher than that of human enamel. Furthermore, the ceramics composed of iron-calcium phosphates show enhanced acid resistance. This study provides a novel route to prepare Fe-ACP, and presents the potential role of Fe-ACP in biomineralization and as starting material to fabricate acid-resistant high-performance bioceramics.

Cross-Linking of Apatite-Gelatin Nanocomposites as the Basis for Dentine Replacement Materials

A novel approach for the production of a bioinspired dentine replacement material is introduced. An apatite-gelatin nanocomposite material was cross-linked with various cross-linkers. These nanocomposites have a high resemblance to mammalian dentine regarding its composition and properties. A precipitation reaction was used to produce apatite-gelatin nanocomposites as starting materials. Cross-linking of the gelatin has to be performed to produce dentine-like and thus tough and robust apatite-gelatin nanocomposites. Therefore, the efficacy of various protein cross-linkers was tested, and the resulting materials were characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and EXAFS as well as CHNS analysis and tested for their mechanical performance using Vickers hardness measurements as well as for their dissolution stability in EDTA. Especially glutaraldehyde, proanthocyanidins, and transglutaminase gave promising results with hardness values of up to 63 HV0.2. To further improve the material properties, we combined the effective cross-linker transglutaminase with casein, which led to an improved interconnection between the single nanocomposite platelets. By doing so, a cross-linked composite was obtained, which shows even higher hardness values than does human dentine, at 76 HV_0.2. The combination of apatite-gelatin nanocomposites with an effective cross-linker resulted in a bioinspired material with composition and properties close to those of human dentine.

Uncovering the Role of Bicarbonate in Calcium Carbonate Formation at Near-Neutral pH

Mechanistic pathways relevant to mineralization are not well‐understood fundamentally, let alone in the context of their biological and geological environments. Through quantitative analysis of ion association at near‐neutral pH, we identify the involvement of HCO₃⁻ ions in CaCO₃ nucleation. Incorporation of HCO₃⁻ ions into the structure of amorphous intermediates is corroborated by solid‐state nuclear magnetic resonance spectroscopy, complemented by quantum mechanical calculations and molecular dynamics simulations. We identify the roles of HCO₃⁻ ions as being through (i) competition for ion association during the formation of ion pairs and ion clusters prior to nucleation and (ii) incorporation as a significant structural component of amorphous mineral particles. The roles of HCO₃⁻ ions as active soluble species and structural constituents in CaCO₃ formation are of fundamental importance and provide a basis for a better understanding of physiological and geological mineralization.

Inorganic Porous Bulk Discs as a Matrix for Thin-Layer Chromatography and Translucent Hard Composite Materials

Magnesium-stabilized amorphous calcium carbonate (Mg-ACC), amorphous magnesium calcium silicate hydrate (MCSH), and hydroxyapatite (HAp) are prepared by a precipitation method. By cold-pressing these particles, it is possible to produce porous bulk discs with a narrow pore size distribution. These porous inorganic discs (Mg-ACC, MCSH, and HAp) are investigated as stationary phases to study the chromatographic behavior and adsorption ability of rhodamine B, methylene blue, and ribonuclease. The adsorption affinities of different biomolecules can be easily observed and evaluated through this method. Furthermore, by infiltrating fabricated opaque porous discs with benzyl ether, which has a similar refractive index as the used inorganic particles (Mg-ACC, MCSH, and HAp), their optical properties significantly change and the discs become translucent. Moreover, by infiltrating the MCSH discs with a light-curing polymer, translucent composites with good surface hardness are fabricated. By doping particles with ions such as Ni²⁺, Co²⁺, Fe³⁺, and Eu³⁺, the color and UV-visible spectrum of the bulk discs can be adjusted. Typically, by using iron-doped MCSH particles as the inorganic matrix, nanocomposites, which show a steep UV-absorption edge at 400 nm, are fabricated. Our work provides a simple and economical method to evaluate the affinity of biomolecules to inorganic materials and a novel way to fabricate translucent hard composite materials. The fabricated nanocomposite discs show a great UV shielding effect and superior surface hardness compared to polymethyl methacrylate and commercial sunglasses, suggesting their potential as new sunglass materials.

On the Future Design of Bio-Inspired Polyetheretherketone Dental Implants

Polyetheretherketone (PEEK) is a promising implant material because of its excellent mechanical characteristics. Although this polymer is a standard material in spinal applications, PEEK is not in use in the manufacturing of dental implants, where titanium is still the most-used material. This may be caused by its relative bio-inertness. By the use of various surface modification techniques, efforts have been made to enhance its osseointegrative characteristics to enable the polymer to be used in dentistry. In this feature paper, the state-of-the-art for dental implants is given and different surface modification techniques of PEEK are discussed. The focus will lie on a covalently attached surface layer mimicking natural bone. The usage of such covalently anchored biomimetic composite materials combines many advantageous properties: A biocompatible organic matrix and a mineral component provide the cells with a surrounding close to natural bone. Bone-related cells may not recognize the implant as a foreign body and therefore, may heal and integrate faster and more firmly. Because neither metal-based nor ceramics are ideal material candidates for a dental implant, the combination of PEEK and a covalently anchored mineralized biopolymer layer may be the start of the desired evolution in dental surgery.

On mechanisms of mesocrystal formation: magnesium ions and water environments regulate the crystallization of amorphous minerals

Elucidating the emergence of crystalline superstructures from amorphous precursors, hydration environments and ionic constituents can guide transformation and structuration reactions towards distinct micro- and nano-structures.

Costs of cloud computing for a biometry department. A case study

BACKGROUND

"Cloud" computing providers, such as the Amazon Web Services (AWS), offer stable and scalable computational resources based on hardware virtualization, with short, usually hourly, billing periods. The idea of pay-as-you-use seems appealing for biometry research units which have only limited access to university or corporate data center resources or grids.

OBJECTIVES

This case study compares the costs of an existing heterogeneous on-site hardware pool in a Medical Biometry and Statistics department to a comparable AWS offer.

METHODS

The "total cost of ownership", including all direct costs, is determined for the on-site hardware, and hourly prices are derived, based on actual system utilization during the year 2011. Indirect costs, which are difficult to quantify are not included in this comparison, but nevertheless some rough guidance from our experience is given. To indicate the scale of costs for a methodological research project, a simulation study of a permutation-based statistical approach is performed using AWS and on-site hardware.

RESULTS

In the presented case, with a system utilization of 25-30 percent and 3-5-year amortization, on-site hardware can result in smaller costs, compared to hourly rental in the cloud dependent on the instance chosen. Renting cloud instances with sufficient main memory is a deciding factor in this comparison.

CONCLUSIONS

Costs for on-site hardware may vary, depending on the specific infrastructure at a research unit, but have only moderate impact on the overall comparison and subsequent decision for obtaining affordable scientific computing resources. Overall utilization has a much stronger impact as it determines the actual computing hours needed per year. Taking this into ac count, cloud computing might still be a viable option for projects with limited maturity, or as a supplement for short peaks in demand.

Application of microarray analysis on computer cluster and cloud platforms

BACKGROUND

Analysis of recent high-dimensional biological data tends to be computationally intensive as many common approaches such as resampling or permutation tests require the basic statistical analysis to be repeated many times. A crucial advantage of these methods is that they can be easily parallelized due to the computational independence of the resampling or permutation iterations, which has induced many statistics departments to establish their own computer clusters. An alternative is to rent computing resources in the cloud, e.g. at Amazon Web Services.

OBJECTIVES

In this article we analyze whether a selection of statistical projects, recently implemented at our department, can be efficiently realized on these cloud resources. Moreover, we illustrate an opportunity to combine computer cluster and cloud resources.

METHODS

In order to compare the efficiency of computer cluster and cloud implementations and their respective parallelizations we use microarray analysis procedures and compare their runtimes on the different platforms.

RESULTS

Amazon Web Services provide various instance types which meet the particular needs of the different statistical projects we analyzed in this paper. Moreover, the network capacity is sufficient and the parallelization is comparable in efficiency to standard computer cluster implementations.

CONCLUSION

Our results suggest that many statistical projects can be efficiently realized on cloud resources. It is important to mention, however, that workflows can change substantially as a result of a shift from computer cluster to cloud computing.

Die Mobilisation des linken Hemikolons von medial

INTRODUCTION

Laparoscopic surgery of the colon is becoming more and more popular. However, regarding sigmoid resection, controversy remains concerning the extent of mobilisation, particularly regarding the splenic flexure. We developed a technique for anterior resection that meets all surgical standards: the anterior approach.

MATERIALS AND METHODS

From October 1999 to March 2001, 50 patients with benign diseases of the colon underwent laparoscopically assisted sigmoid resection. A completely anterior approach for mobilisation of the left hemicolon was used in all cases. Positioning the patients in Trendelenburg position on the extreme right side enabled primary ligation of the inferior mesenteric vein and artery as well as complete mobilisation of the splenic flexure from the middle. A transanal circular stapling device was used to reanastomose the colon 10-12 cm from the anus.

RESULTS

There were conversion and complication rates of 10% each, and three patients needed to be reoperated. The median operating time was 180 min. Patients could be dismissed on the 14th postoperative day.

CONCLUSION

To establish an operative standard, this technique has so far been used only for benign colon diseases. According to our experience, we think that it meets all oncological standards. Use of this technique in the treatment of malignant diseases seems therefore justified.

The urinary bladder angiotensin system: response to infusions of angiotensin I and angiotensin-converting enzyme inhibitors

The circulating and urinary bladder tissue concentrations of angiotensin I (ANG I) and angiotensin II [ANG-(1-8)] were examined in anesthetized Sprague-Dawley male rats given an intravenous bolus infusion of either ANG I, the angiotensin-converting enzyme (ACE) inhibitors enalaprilat or ramiprilat, or saline. The mean concentrations of ANG I and ANG-(1-8) were markedly higher in the urinary bladder tissue than in whole blood. There was a significant increase in the concentration of ANG I and ANG-(1-8), both in the urinary bladder tissue and the circulation, after the ANG I infusion. Both ACE inhibitors were associated with an increase in the concentration of whole blood ANG I; however, tissue ANG I levels were significantly increased only following ACE inhibition with ramiprilat but not with enalaprilat. Both plasma and urinary bladder tissue ANG-(1-8) levels decreased significantly following ACE inhibition, but only with ramiprilat. The elevated urinary bladder tissue levels of ANG I and ANG-(1-8) at baseline, compared with circulating levels, and the maintenance of ANG-(1-8) in bladder tissue in the face of inhibition of the circulatory renin-angiotensin system with enalaprilat support the presence of an autocrine/paracrine renin-angiotensin system in the urinary bladder. Under the current experimental conditions, ramiprilat appears to have enhanced bladder activity compared with enalaprilat.

[Bisphosphonate therapy of Paget's disease of bone with pamidronate]

BACKGROUND

Paget's disease of bone is a disease with massive focal increase of bone turnover. Bisphosphonates like etidronate inhibit of osteoclastic bone resorption and are therefore established in the treatment of Paget's disease. The aminobisphosphonate pamidronate is 100 times more potent than etidronate. To assess the therapeutic potential for Paget's disease, we have investigated the long-term efficacy of two different dosages of pamidronate.

PATIENTS AND METHODS

40 consecutive patients with Paget's disease received a total dose of either 180 mg (n = 21) or 100 mg (n = 19) of pamidronate i.v. over 9 or 5 days respectively in two independent phases of a prospective trial. Efficacy and side effects were monitored for a follow up period of up to two years.

RESULTS

For both dosages a significant reduction of urinary 24-h-hydroxyprolin excretion and serum alkaline phosphatase (AP) levels as parameters of disease activity was recorded. AP levels fell to a minimum of 31 +/- 3% (180 mg) and 41 +/- 5% (100 mg) of pretreatment values, respectively. Two years after treatment, a significant reduction of disease activity could still be detected. Side effects, including transient fever, head ache or bone pain occurred in one third of the patients.

CONCLUSION

Pamidronate treatment for Paget's disease of bone leads to a sustained inhibition of elevated bone turnover.

Glomerular function and structure in the sodium-replete and sodium-deplete uninephrectomized spontaneously hypertensive rat: effect of blood pressure reduction, glomerular structure, and blood pressure reduction

To assess the effects of chronic dietary sodium restriction and blood pressure reduction on glomerular function and structure during the pathogenesis of hypertensive renal disease, experiments were conducted in uninephrectomized (UNX) spontaneously hypertensive rats (SHR) using the dihydropyridine calcium antagonist manidipine. Male SHRs underwent UNX at age 10-11 weeks and subsequently were assigned to one of four groups: sodium-replete (0.4%); sodium-replete and a predetermined antihypertensive dose of manidipine (20 mg/kg body weight); sodium-deplete (0.09%); and sodium-deplete and manidipine (20 mg/kg body weight). Twelve weeks later, renal morphologic and functional studies were performed. Sodium restriction had no significant effect on systolic blood pressure, but creatinine clearance and urinary protein excretion were decreased. Importantly, mean glomerular volume and the prevalence of mesangial expansion were lower with sodium restriction. This occurred in the presence of high concentrations of plasma and renal tissue angiotensin II. Manidipine significantly reduced systolic blood pressure in the sodium-replete and sodium-deplete UNX-SHRs. This therapy was not associated with significant changes in creatinine clearance and urinary protein excretion in the sodium-deplete or sodium-replete UNX-SHRs. The prevalence of mesangial expansion in the sodium-replete UNX-SHR was approximately 50% lower with manidipine. Plasma and renal tissue angiotensin II concentrations were not affected by the drug. In the sodium-deplete UNX-SHR, the prevalence of mesangial expansion was not reduced further by manidipine. However, plasma and renal tissue angiotensin II concentrations were increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative catheter thrombolysis as an adjunct to surgical revascularisation for infrainguinal limb-threatening ischaemia

The objective of this study was to assess the benefits of intraoperative thrombolysis (IOL) on patients with acute leg ischaemia. This study was conducted in the Department of Cardiovascular Surgery, Inselspital, Berne, Switzerland. IOL was prospectively assessed in 25 patients with infrainguinal limb-threatening ischaemia due to acute thrombosis of atherosclerotic lesions and aneurysms (44%), occluded grafts (32%), arterial injuries (12%), delayed embolism (8%) and trash foot (8%). Three hundred and seventy-five thousand units of urokinase were delivered over 30 min with inflow occlusion to the profunda femoral artery in 8%, to the calf arteries via exposed trifurcation in 88% and to the pedal arch via exposed posterior tibial artery at the ankle in 8% of the patients. This was followed by graft thrombectomy in 24%, femoropopliteal bypass in 60%, intraoperative percutaneous transluminal angioplasty in 12% and vein patch angioplasty in 16%. Chief outcome measures were: postoperative morbidity; mortality; patency and limb salvage up to a maximum of 2 years. Postoperative bleeding complications occurred in two patients (8%) and consisted of two wound haematomas. Four patients died within 30 days after IOL, but no death could be attributed to IOL. All remaining patients were followed with a mean follow-up time of 10.9 months. The patency and limb salvage rate remained stable at 71 and 86% after 6 and 2 months, respectively. Conclusions were that IOL followed by surgical inflow restoration is a straightforward procedure for limb-threatening ischaemia with rewarding results regarding side effects, patency and limb salvage.