Designing Biostable Polyurethane Elastomers for Biomedical Implants

2003 ◽  
Vol 56 (6) ◽  
pp. 545 ◽  
Author(s):  
Pathiraja A. Gunatillake ◽  
Darren J. Martin ◽  
Gordon F. Meijs ◽  
Simon J. McCarthy ◽  
Raju Adhikari
Keyword(s):  
Chemical Structure ◽  
Oxidative Degradation ◽  
In Vivo Studies ◽  
Biomedical Implants ◽  
Polyurethane Elastomers ◽  
Structure Synthesis ◽  
Synthesis Properties ◽  
The Stability

The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly(tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved long-term biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.

scholarly journals Time-Programmed Delivery of Sorafenib and Anti-CD47 Antibody via a Double-Layer-Gel Matrix for Postsurgical Treatment of Breast Cancer

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Liping Huang ◽  
Yiyi Zhang ◽  
Yanan Li ◽  
Fanling Meng ◽  
Hongyu Li ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Near Infrared ◽  
Immune Escape ◽  
Regulatory Protein ◽  
In Vivo Studies ◽  
Breast Cancer Patients ◽  
Thermally Responsive ◽  
Immunosuppressive Microenvironment

AbstractThe highly immunosuppressive microenvironment after surgery has a crucial impact on the recurrence and metastasis in breast cancer patients. Programmable delivery of immunotherapy-involving combinations through a single drug delivery system is highly promising, yet greatly challenging, to reverse postoperative immunosuppression. Here, an injectable hierarchical gel matrix, composed of dual lipid gel (DLG) layers with different soybean phosphatidylcholine/glycerol dioleate mass ratios, was developed to achieve the time-programmed sequential delivery of combined cancer immunotherapy. The outer layer of the DLG matrix was thermally responsive and loaded with sorafenib-adsorbed graphene oxide (GO) nanoparticles. GO under manually controlled near-infrared irradiation generated mild heat and provoked the release of sorafenib first to reeducate tumor-associated macrophages (TAMs) and promote an immunogenic tumor microenvironment. The inner layer, loaded with anti-CD47 antibody (aCD47), could maintain the gel state for a much longer time, enabling the sustained release of aCD47 afterward to block the CD47-signal regulatory protein α (SIRPα) pathway for a long-term antitumor effect. In vivo studies on 4T1 tumor-bearing mouse model demonstrated that the DLG-based strategy efficiently prevented tumor recurrence and metastasis by locally reversing the immunosuppression and synergistically blocking the CD47-dependent immune escape, thereby boosting the systemic immune responses.

scholarly journals Long Term Pharmacological Perturbation of Autophagy in Mice: Are HCQ Injections a Relevant Choice?

Biomedicines ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 47 ◽  
Author(s):  
Jean-Daniel Masson ◽  
Benoit Blanchet ◽  
Baptiste Periou ◽  
François-Jérôme Authier ◽  
Baharia Mograbi ◽  
...  
Keyword(s):  
Mouse Models ◽  
In Vivo Studies ◽  
Loss Of Function ◽  
Evolutionarily Conserved ◽  
Atg Genes ◽  
Conditional Inhibition ◽  
The Impact ◽  
Catabolic Process

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved catabolic process whose loss-of-function has been linked to a growing list of pathologies. Knockout mouse models of key autophagy genes have been instrumental in the demonstration of the critical functions of autophagy, but they display early lethality, neurotoxicity and unwanted autophagy-independent phenotypes, limiting their applications for in vivo studies. To avoid problems encountered with autophagy-null transgenic mice, we investigated the possibility of disturbing autophagy pharmacologically in the long term. Hydroxychloroquine (HCQ) ip injections were done in juvenile and adult C57bl/6j mice, at range doses adapted from the human malaria prophylactic treatment. The impact on autophagy was assessed by western-blotting, and juvenile neurodevelopment and adult behaviours were evaluated for four months. Quite surprisingly, our results showed that HCQ treatment in conditions used in this study neither impacted autophagy in the long term in several tissues and organs nor altered neurodevelopment, adult behaviour and motor capabilities. Therefore, we recommend for future long-term in vivo studies of autophagy, to use genetic mouse models allowing conditional inhibition of selected Atg genes in appropriate lineage cells instead of HCQ treatment, until it could be successfully revisited using higher HCQ doses and/or frequencies with acceptable toxicity.

scholarly journals 3D-bioprinted tracheal reconstruction: an overview

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Lidia Frejo ◽  
Daniel A. Grande
Keyword(s):  
In Vivo Studies ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Tracheal Reconstruction ◽  
Airway Reconstruction ◽  
Life Threatening ◽  
Scaffold Materials ◽  
Cellular Types

Abstract Congenital tracheomalacia and tracheal stenosis are commonly seen in premature infants. In adulthood, are typically related with chronic obstructive pulmonary disease, and can occur secondarily from tracheostomy, prolong intubation, trauma, infection and tumors. Both conditions are life-threatening when not managed properly. There are still some surgical limitations for certain pathologies, however tissue engineering is a promising approach to treat massive airway dysfunctions. 3D-bioprinting have contributed to current preclinical and clinical efforts in airway reconstruction. Several strategies have been used to overcome the difficulty of airway reconstruction such as scaffold materials, construct designs, cellular types, biologic components, hydrogels and animal models used in tracheal reconstruction. Nevertheless, additional long-term in vivo studies need to be performed to assess the efficacy and safety of tissue-engineered tracheal grafts in terms of mechanical properties, behavior and, the possibility of further stenosis development.

Nontoxic Silicon Nanocrystals and Nanodiamonds as Substitution for Harmful Quantum Dots

2009 ◽  
Vol 1241 ◽  
Author(s):  
Anna Fucikova ◽  
Jan Valenta ◽  
Ivan Pelant ◽  
Vitezslav Brezina
Keyword(s):  
Quantum Dots ◽  
Chemical Composition ◽  
Silicon Nanocrystals ◽  
Nanocrystalline Silicon ◽  
Semiconductor Quantum Dots ◽  
In Vivo Studies ◽  
Long Term Stability

AbstractThe commercially available semiconductor quantum dots have been proven to be slightly to significantly toxic by recent publications depending on the chemical composition. We are developing new non-toxic fluorescent labels based on (i) nanocrystalline silicon, suitable for in vivo studies due to their biodegrability, and on (ii) nanodiamonds, intended mainly for in vitro use due to their long-term stability and nondegradilibity.

Biomechanical Consequences of Total Plantar Fasciotomy

2009 ◽  
Vol 99 (5) ◽  
pp. 422-430 ◽  
Author(s):  
Jo L. Tweed ◽  
Mike R. Barnes ◽  
Mike J. Allen ◽  
Jackie A. Campbell
Keyword(s):  
Center Of Pressure ◽  
Plantar Fascia ◽  
In Vivo Studies ◽  
Medial Longitudinal Arch ◽  
Foot Structure ◽  
Longitudinal Arch ◽  
Plantar Fasciotomy ◽  
Postoperative Problems

Background: Plantar fascia release for chronic plantar fasciitis has provided excellent pain relief and rapid return to activities with few reported complications. Cadaveric studies have led to the identification of some potential postoperative problems, most commonly weakness of the medial longitudinal arch and pain in the lateral midfoot. Methods: An electronic search was conducted of the MEDLINE, ScienceDirect, SportDiscus, EMBASE, CINAHL, Cochrane, and AMED databases. The keywords used to search these databases were plantar fasciotomy and medial longitudinal arch. Articles published between 1976 and 2008 were identified. Results: Collectively, results of cadaveric studies suggested that plantar fasciotomy leads to loss of integrity of the medial longitudinal arch and that total plantar fasciotomy is more detrimental to foot structure than is partial fasciotomy. In vivo studies, although limited in number, concluded that although clinical outcomes were satisfactory, medial longitudinal arch height decreased and the center of pressure of the weightbearing foot was excessively medially deviated postoperatively. Conclusions: Plantar fasciotomy, in particular total plantar fasciotomy, may lead to loss of stability of the medial longitudinal arch and abnormalities in gait, in particular an excessively pronated foot. Further in vivo studies on the long-term biomechanical effects of plantar fasciotomy are required. (J Am Podiatr Med Assoc 99(5): 422–430, 2009)

scholarly journals The behaviour of thiomolybdates in in vitro systems

1979 ◽  
Vol 41 (2) ◽  
pp. 403-405 ◽  
Author(s):  
K. M. Weber ◽  
D. D. Leaver ◽  
A. G. Wedd
Keyword(s):  
Copper Metabolism ◽  
Hydrogen Ion ◽  
In Vivo Studies ◽  
In Vitro Systems ◽  
The Stability

The stability of potassium tetrathiomolybdate was studied in vitro using solutions with molybdenum, hydrogen ion and phosphate concentrations similar to those normally found in the rumen. Under these conditions K2[MoS4] hydrolysed rapidly and as a result the solution contained [MoS4]2−, [MoOS3]2−, [MoO2S2]2−, [HS]− and H2S in equilibrium. In view of this hydrolysis, in vivo studies of thiomolybdate on copper metabolism of sheep should not exclude the possibility that either sulphide or molybdate is responsible for any observed effect.

In vivo studies of the long-term 51Cr red cell survival of serologically incompatible red cell units

Transfusion ◽  
1985 ◽  
Vol 25 (1) ◽  
pp. 34-38 ◽  
Author(s):  
ML Baldwin ◽  
PM Ness ◽  
C Barrasso ◽  
TS Kickler ◽  
H Drew ◽  
...  
Keyword(s):  
Cell Survival ◽  
In Vivo Studies ◽  
Red Cell ◽  
Red Cell Survival

scholarly journals Spatiotemporal evaporating droplet dynamics on fomites enhances long term bacterial pathogenesis

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Sreeparna Majee ◽  
Atish Roy Chowdhury ◽  
Roven Pinto ◽  
Ankur Chattopadhyay ◽  
Amey Nitin Agharkar ◽  
...  
Keyword(s):  
Holistic Approach ◽  
Moisture Stress ◽  
In Vivo Studies ◽  
Drying Process ◽  
Droplet Dynamics ◽  
Contaminated Food ◽  
Induced Flow ◽  
Gut Pathogen

AbstractNaturally drying bacterial droplets on inanimate surfaces representing fomites are the most consequential mode for transmitting infection through oro-fecal route. We provide a multiscale holistic approach to understand flow dynamics induced bacterial pattern formation on fomites leading to pathogenesis. The most virulent gut pathogen, Salmonella Typhimurium (STM), typically found in contaminated food and water, is used as model system in the current study. Evaporation-induced flow in sessile droplets facilitates the transport of STM, forming spatio-temporally varying bacterial deposition patterns based on droplet medium’s nutrient scale. Mechanical and low moisture stress in the drying process reduced bacterial viability but interestingly induced hyper-proliferation of STM in macrophages, thereby augmenting virulence in fomites. In vivo studies of fomites in mice confirm that STM maintains enhanced virulence. This work demonstrates that stressed bacterial deposit morphologies formed over small timescale (minutes) on organic and inorganic surfaces, plays a significant role in enhancing fomite’s pathogenesis over hours and days.

scholarly journals Nanoagents for improving focused ultrasound thermal delivery to tumors with imaging feedback

2018 ◽  
Author(s):  
Paul Dayton
Keyword(s):  
Spatial Distribution ◽  
Focused Ultrasound ◽  
Near Field ◽  
Tumor Model ◽  
In Vivo Studies ◽  
Hifu Treatment ◽  
Hifu Ablation ◽  
Delivery Efficiency

We have developed a unique metastable nanodroplet formulation which data suggests 1) will improve thermal delivery efficiency of intensity focused ultrasound (HIFU) ablation in vivo, and 2) will improve the spatial distribution of thermal delivery at the acoustic focus, without near-field attenuation or heating. In this project, we will test and optimize our approach by quantifying nanodroplet dose and improvements in thermal delivery efficiency in vivo using MRgFUS; assessing long term circulation in vivo; and by performing MRgFUS in vivo studies in rodent tumor model to validate nanodropletenhanced HIFU treatment of tumors, compared to sham controls. Finally, we will perform histology to assess tissue for collateral bioeffects.

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