Interface biomechanics of the Anca Dual Fit hip stem: An in vitro experimental study

2001 ◽  
Vol 215 (6) ◽  
pp. 555-564 ◽  
Author(s):  
L Monti ◽  
L Cristofolini ◽  
M Viceconti
Keyword(s):  
Load Transfer ◽  
Bone Ingrowth ◽  
Stress Shielding ◽  
Primary Stability ◽  
Stair Climbing ◽  
Term Stability ◽  
Long Term Stability ◽  
Cemented Stem

The Anca Dual Fit hip stem (Cremascoli Wright, Milan, Italy) is a partially cemented stem developed to overcome the drawbacks of both cemented and uncemented fixations. Its design was based on the hypothesis that partial cementing would ensure the primary stability necessary to allow bone ingrowth on the cement-free stem surfaces. At the same time, the limitation of the cement to the proximal regions would prevent stress-shielding by increasing proximal load transfer. After finite element (FE) simulations and in vitro primary stability assessment, an analysis of the long-term stability of the Anca Dual Fit stem was necessary to conclude the preclinical testing. Three stems were implanted in composite femurs and subjected to testing for 1 × 106 cycles, each cycle reproducing the activity of stair climbing. The simulation was designed so as to replicate the physiological loading in a simplified, yet relevant way for this test. Various measurements were collected before, during and after the test in order to give exhaustive information on the response of the implant to long-term, cyclic loading. The present study confirmed the positive results of previous investigations, and proved that the Anca Dual Fit stem has excellent long-term stability; therefore successful clinical outcomes are predicted.

scholarly journals Long-Term Stability of a RAFT-Modified Bulk-Fill Resin-Composite under Clinically Relevant versus ISO-Curing Conditions

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5350
Author(s):  
Niklas Graf ◽  
Nicoleta Ilie
Keyword(s):  
Fracture Mechanism ◽  
Resin Composite ◽  
Bending Test ◽  
Depth Sensing ◽  
Matrix Formulation ◽  
Curing Conditions ◽  
Term Stability ◽  
Long Term Stability

The addition of RAFT (reversible addition-fragmentation chain transfer) agents to the matrix formulation of a bulk-fill resin composite can significantly decrease the required curing time down to a minimum of 3 s. Evaluating the long term-stability of this resin composite in relation to varied curing conditions in an in-vitro environment was this study’s goal. Specimens were produced according to either an ISO or one of two clinical curing protocols and underwent a maximum of three successive aging procedures. After each one of the aging procedures, 30 specimens for each curing condition were extracted for a three-point bending test. Fragments were then stereo-microscopically characterized according to their fracture mechanism. Weibull analysis was used to quantify the reliability of each aging and curing combination. Selected fragments (n = 12) underwent further testing via depth-sensing indentation. Mechanical values for either standardized or clinical curing were mostly comparable. However, changes in fracture mechanism and Weibull modulus were observed after each aging procedure. The final procedure exposed significant differences in the mechanical values due to curing conditions. Curing conditions with increased radiant exposure seemingly result in a higher crosslink in the polymer-matrix, thus increasing resistance to aging. Yet, the clinical curing conditions still resulted in acceptable mechanical values, proving the effectiveness of RAFT-polymerization.

Long- and short-term in vitro D-dimer stability measured with INNOVANCE D-Dimer

2010 ◽  
Vol 103 (02) ◽  
pp. 461-465 ◽  
Author(s):  
Martina Böhm-Weigert ◽  
Thomas Wissel ◽  
Heidrun Muth ◽  
Bettina Kemkes-Matthes ◽  
Dirk Peetz
Keyword(s):  
Frozen Storage ◽  
Percentage Change ◽  
Short Term ◽  
Term Stability ◽  
Long Term Stability ◽  
Repeated Freezing ◽  
The Mean ◽  
D Dimer

Summary In vitro D-dimer stability in plasma is widely assumed, but has not yet been documented by systematic studies using samples covering a wide range of D-dimer. We investigated the short- and long-term stability of D-dimer in clinical citrated plasma samples with normal and pathological levels. The short-term stability was analysed by measuring D-dimer fresh, after storage of plasma for 4 hours at room temperature (RT) and after an additional 24 h storage at +2 to +8°C (n=40). Long-term stability samples (n=40) were measured fresh and after storage for 19, 25 and 36 months at ≤-60°C. The effect of repeated freezing was analysed by measuring samples (n=50) fresh and after four consecutive freeze-thaw cycles. D-dimer was measured on the BCS System using the INNOVANCE D-Dimer assay (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). D-dimer values at baseline ranged from 0.23–22.2 mg/l FEU. The mean percentage change after storage for 4 hours at RT and additional 24 hours at +2 to +8°C was +3.8% and +2.7%, respectively. The mean percentage change after frozen storage for 19, 25 and 36 months at ≤-60°C was –11.7%, –4.8% and –9.3%, respectively. The small decrease of D-dimer values after frozen storage was not time-dependent. Repeated freezing did not significantly alter D-dimer values (mean change ≤5%). The data demonstrate stability of D-dimer in plasma prior to freezing for up to 4 hours at RT and for up to 24 hours at +2 to +8°C as well as in plasma stored for up to three years at ≤-60°C.

Nanocrystalline Tetracalcium Phosphate Cement

2004 ◽  
Vol 83 (5) ◽  
pp. 425-428 ◽  
Author(s):  
U. Gbureck ◽  
J.E. Barralet ◽  
M.P. Hofmann ◽  
R. Thulĺ
Keyword(s):  
Calcium Hydroxide ◽  
High Energy ◽  
In Vitro Test ◽  
Ion Release ◽  
Tetracalcium Phosphate ◽  
Term Stability ◽  
Long Term Stability ◽  
Hydroxyl Ion

Calcium hydroxide cements can lack long-term stability and achieve sustained release by matrix-controlled diffusion of hydroxyl ions. Tetracalcium phosphate (TTCP) hydrolyzes slowly to form calcium hydroxide and a thin insoluble apatite layer that prevents further reaction. In this study, mechanical amorphization was used to create a setting calcium-hydroxide-releasing cement from TTCP. The effect of high-energy ball milling of TTCP on the mechanical properties of the cement was investigated. X-ray diffraction data were used to determine the phase composition of the set cements. An accelerated in vitro test compared pH of water after prolonged boiling of nanocrystalline TTCP cements and a calcium salicylate material. As milling time increased, cement compressive strength and degree of conversion increased. Hydroxyl ion release from the cement was comparable with that from a calcium salicylate material. This new cement system offers the antimicrobial potential of calcium salicylate materials combined with the long-term stability of insoluble apatite cements.

scholarly journals Stability Assessment of Four Chimeric Proteins for Human Chagas Disease Immunodiagnosis

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 289
Author(s):  
Paola Alejandra Fiorani Celedon ◽  
Leonardo Maia Leony ◽  
Ueriton Dias Oliveira ◽  
Natália Erdens Maron Freitas ◽  
Ângelo Antônio Oliveira Silva ◽  
...  
Keyword(s):  
Chagas Disease ◽  
Structural Integrity ◽  
Structural Characteristics ◽  
Control Group ◽  
Stability Tests ◽  
Adverse Conditions ◽  
Term Stability ◽  
Long Term Stability

The performance of an immunoassay relies on antigen-antibody interaction; hence, antigen chemical stability and structural integrity are paramount for an efficient assay. We conducted a functional, thermostability and long-term stability analysis of different chimeric antigens (IBMP), in order to assess effects of adverse conditions on four antigens employed in ELISA to diagnose Chagas disease. ELISA-based immunoassays have served as a model for biosensors development, as both assess molecular interactions. To evaluate thermostability, samples were heated and cooled to verify heat-induced denaturation reversibility. In relation to storage stability, the antigens were analyzed at 25 °C at different moments. Long-term stability tests were performed using eight sets of microplates sensitized. Antigens were structurally analyzed through circular dichroism (CD), dynamic light scattering, SDS-PAGE, and functionally evaluated by ELISA. Data suggest that IBMP antigens are stable, over adverse conditions and for over a year. Daily analysis revealed minor changes in the molecular structure. Functionally, IBMP-8.2 and IBMP-8.3 antigens showed reactivity towards anti-T. cruzi antibodies, even after 72 h at 25 °C. Long-term stability tests showed that all antigens were comparable to the control group and all antigens demonstrated stability for one year. Data suggest that the antigens maintained their function and structural characteristics even in adverse conditions, making them a sturdy and reliable candidate to be employed in future in vitro diagnostic tests applicable to different models of POC devices, such as modern biosensors in development.

Robust oil-core nanocapsules with hyaluronate-based shells as promising nanovehicles for lipophilic compounds

Nanoscale ◽  
2017 ◽  
Vol 9 (47) ◽  
pp. 18867-18880 ◽  
Author(s):  
Joanna Szafraniec ◽  
Agnieszka Błażejczyk ◽  
Edyta Kus ◽  
Małgorzata Janik ◽  
Gabriela Zając ◽  
...  
Keyword(s):  
Lipophilic Compounds ◽  
Term Stability ◽  
Long Term Stability ◽  
Free Process

Biocompatible hyaluronate-based nanocapsules with liquid oil cores exhibiting long-term stability and tunable size were obtained in a versatile surfactant-free process and their biodistribution was studied in vivo and in vitro.

scholarly journals Comparison of the Efficacy of Two Novel Antitubercular Agents in Free and Liposome-Encapsulated Formulations

2021 ◽  
Vol 22 (5) ◽  
pp. 2457
Author(s):  
Nikoletta Kósa ◽  
Ádám Zolcsák ◽  
István Voszka ◽  
Gabriella Csík ◽  
Kata Horváti ◽  
...  
Keyword(s):  
Cellular Uptake ◽  
Drug Carrier ◽  
Antimycobacterial Activity ◽  
Size Exclusion ◽  
In Silico Docking ◽  
Term Stability ◽  
Long Term Stability

Tuberculosis is one of the top ten causes of death worldwide, and due to the appearance of drug-resistant strains, the development of new antituberculotic agents is a pressing challenge. Employing an in silico docking method, two coumaran (2,3-dihydrobenzofuran) derivatives—TB501 and TB515—were determined, with promising in vitro antimycobacterial activity. To enhance their effectiveness and reduce their cytotoxicity, we used liposomal drug carrier systems. Two types of small unilamellar vesicles (SUV) were prepared: multicomponent pH-sensitive stealth liposome (SUVmixed) and monocomponent conventional liposome. The long-term stability of our vesicles was obtained by the examination of particle size distribution with dynamic light scattering. Encapsulation efficiency (EE) of the two drugs was determined from absorption spectra before and after size exclusion chromatography. Cellular uptake and cytotoxicity were determined on human MonoMac-6 cells by flow cytometry. The antitubercular effect was characterized by the enumeration of colony-forming units on Mycobacterium tuberculosis H37Rv infected MonoMac-6 cultures. We found that SUVmixed + TB515 has the best long-term stability. TB515 has much higher EE in both types of SUVs. Cellular uptake for native TB501 is extremely low, but if it is encapsulated in SUVmixed it appreciably increases; in the case of TB515, quasi total uptake is accessible. It is concluded that SUVmixed + TB501 seems to be the most efficacious antitubercular formulation given the presented experiments; to find the most promising antituberculotic formulation for therapy further in vivo investigations are needed.

Load transfer in the proximal femur and primary stability of a cemented and uncemented femoral stem: An experimental study on cadaver femurs

2017 ◽  
Vol 231 (12) ◽  
pp. 1195-1203 ◽  
Author(s):  
Cathrine H Enoksen ◽  
Tina S Wik ◽  
Jomar Klaksvik ◽  
Astvaldur J Arthursson ◽  
Otto S Husby ◽  
...  
Keyword(s):  
Proximal Femur ◽  
Load Transfer ◽  
Femoral Stem ◽  
Primary Stability ◽  
The Elderly ◽  
Stair Climbing ◽  
Physiological Strain ◽  
Fixation Methods ◽  
Cemented Stem ◽  
Total Point

There are principally two fixation methods in total hip arthroplasty, cemented and uncemented. Both methods have in general good long-time survival. Studies comparing cemented and uncemented femoral stems indicate that the cemented stems perform somewhat better, at least in the elderly population. The aim of this study was to compare load transfer and the initial micromotion pattern for an uncemented and a cemented stem. A total of 12 human cadavers were tested in a hip simulator during single leg and stair climbing. Strain was measured on the proximal femur before and after implantation of the prostheses, and the values were presented as percentage of physiological strain. The micromovements between the stem and bone were measured and a total point motion was calculated. The results showed small statistically significant differences between the fixation methods, the largest difference being 8.1 percentage points. The uncemented stem had somewhat higher micromotion than the cemented stem, but less than 10 µm. Both stems thus had acceptable primary stability. The main finding of this study is the strain and micromotion pattern of a cemented and an uncemented stem of similar geometry is overall equal. There were small statistical significant differences between the two fixation methods regarding strain and micromotion levels. The differences are considered too small to be clinically relevant.

Polydopamine nanoparticles' activity and long-term stability should be fully studied for gene therapy applications

2021 ◽  
Author(s):  
Moataz Dowaidar
Keyword(s):  
Structural Control ◽  
Thrombus Formation ◽  
Contact Process ◽  
Protein Corona ◽  
Structure Property ◽  
Term Stability ◽  
Long Term Stability

Many substantial hurdles must be solved for in vivo or in vitro clinical translation of the Polydopamine (PDA)-based nanomaterials. Excessive accumulation of residual unreacted DA and specific metabolites (DA or other small molecules) of PDA in vivo may trigger a possible syndrome of dopamine dysregulation characterized by addictive behaviour, as DA may act as an endogenous neurotoxin when its vesicular sequestration is dysregulated. PDA nanoparticles' activity and long-term stability should be fully studied for in vivo applications aside from probable toxicity. According to the findings, PDA's strong reactivity with numerous functional groups (catechol, quinone, and amine) is comparatively favorable, but in mild circumstances it may have negative effects on the organism owing to direct alcohol interactions. More crucially, the charged, moist adhesive PDA has a high affinity for protein attachment, which might be a major defect in the blood contact process. Direct blood contact with these PDA-based nanomaterials with high specific surface area would result in fast protein adsorption, the establishment of a "protein corona" within minutes, and increased thrombus formation risk. In vitro applications, on the other hand, can prevent the threat of detrimental cell or tissue effects. New rules, theories and processes on structure property performance relationships may be developed by researching the in vivo bioapplications of the above-mentioned PDA nanoarchitectures, possibly leading to fundamental and useful insights into in-vitro material translations. Despite the fact that major impediments to structural control persist, it is predicted that in the future, electron coupling will bring new answers to challenges of improved illness diagnosis and therapy.

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